Matteo Cargnello

All Publications

• A General Approach for Metal Nanoparticle Encapsulation Within Porous Oxides. Advanced materials (Deerfield Beach, Fla.) Zhou, C., Oh, J., Stone, M. L., Richardson, S., Chung, P. H., Osio-Norgaard, J., Nhan, B. T., Kumar, A., Chi, M., Cargnello, M. 2024: e2409710

  Abstract

  Encapsulation of metal nanoparticles within oxide materials has been shown as an effective strategy to improve activity, selectivity, and stability in several catalytic applications. Several approaches have been proposed to encapsulate nanoparticles, such as forming core-shell structures, growing ordered structures (zeolites or metal-organic frameworks) on nanoparticles, or directly depositing support materials on nanoparticles. Here, a general nanocasting method is demonstrated that can produce diverse encapsulated metal@oxide structures with different compositions (Pt, Pd, Rh) and multiple types of oxides (Al2O3, Al2O3-CeO2, ZrO2, ZnZrOx, In2O3, Mn2O3, TiO2) while controlling the size and dispersion of nanoparticles and the porous structure of the oxide. Metal@polymer structures are first prepared, and then the oxide precursor is infiltrated into such structures and the resulting material is calcined to form the metal@oxide structures. Most Pt@oxides catalysts show similar catalytic activity, demonstrating the availability of surface Pt sites in the encapsulated structures. However, the Pt@Mn2O3 sample showed much higher CO oxidation activity, while also being stable under aging conditions. This work demonstrated a robust nanocasting method to synthesize metal@oxide structures, which can be utilized in catalysis to finely tune metal-oxide interfaces.

  View details for DOI 10.1002/adma.202409710

  View details for PubMedID 39523738

• Dynamic Behavior of Pt Multimetallic Alloys for Active and Stable Propane Dehydrogenation Catalysts. Journal of the American Chemical Society Werghi, B., Saini, S., Chung, P. H., Kumar, A., Ebrahim, A. M., Abels, K., Chi, M., Abild-Pedersen, F., Bare, S. R., Cargnello, M. 2024

  Abstract

  Improving the use of platinum in propane dehydrogenation catalysts is a crucial aspect to increasing the efficiency and sustainability of propylene production. A known and practiced strategy involves incorporating more abundant metals in supported platinum catalysts, increasing its activity and stability while decreasing the overall loading. Here, using colloidal techniques to control the size and composition of the active phase, we show that Pt/Cu alloy nanoparticles supported on alumina (Pt/Cu/Al2O3) displayed elevated rates for propane dehydrogenation at low temperature compared to a monometallic Pt/Al2O3 catalyst. We demonstrate that the enhanced catalytic activity is correlated with a higher surface Cu content and formation of a Pt-rich core and Cu-rich shell that isolates Pt sites and increases their intrinsic activity. However, rates declined on stream because of dynamic metal diffusion processes that led to a more uniform alloy structure. This transformation was only partially inhibited by adding excess hydrogen to the feed stream. Instead, cobalt was introduced to provide trimetallic Pt/Cu/Co catalysts with stabilized surface structure and stable activity and higher rates than the original Pt/Cu system. The structure-activity relationship insights in this work offer improved knowledge of propane dehydrogenation catalyst development featuring reduced Pt loadings and notable thermal stability for propylene production.

  View details for DOI 10.1021/jacs.4c09424

  View details for PubMedID 39475575

• A Career in Catalysis: Raymond J. Gorte ACS CATALYSIS Abdelrahman, O. A., Altman, E. I., Cargnello, M., Fornasiero, P., Kim, G., Kungas, R., Luo, J., McIntosh, S., Oh, T., Onn, T., Vohs, J. M. 2024

  View details for DOI 10.1021/acscatal.4c02998

  View details for Web of Science ID 001291127600001

• Unveiling the Stability of Encapsulated Pt Catalysts Using Nanocrystals and Atomic Layer Deposition. Journal of the American Chemical Society Liccardo, G., Cendejas, M. C., Mandal, S. C., Stone, M. L., Porter, S., Nhan, B. T., Kumar, A., Smith, J., Plessow, P. N., Cegelski, L., Osio-Norgaard, J., Abild-Pedersen, F., Chi, M., Datye, A. K., Bent, S. F., Cargnello, M. 2024

  Abstract

  Platinum exhibits desirable catalytic properties, but it is scarce and expensive. Optimizing its use in key applications such as emission control catalysis is important to reduce our reliance on such a rare element. Supported Pt nanoparticles (NPs) used in emission control systems deactivate over time because of particle growth in sintering processes. In this work, we shed light on the stability against sintering of Pt NPs supported on and encapsulated in Al2O3 using a combination of nanocrystal catalysts and atomic layer deposition (ALD) techniques. We find that small amounts of alumina overlayers created by ALD on preformed Pt NPs can stabilize supported Pt catalysts, significantly reducing deactivation caused by sintering, as previously observed by others. Combining theoretical and experimental insights, we correlate this behavior to the decreased propensity of oxidized Pt species to undergo Ostwald ripening phenomena because of the physical barrier imposed by the alumina overlayers. Furthermore, we find that highly stable catalysts can present an abundance of under-coordinated Pt sites after restructuring of both Pt particles and alumina overlayers at a high temperature (800 °C) in C3H6 oxidation conditions. The enhanced stability significantly improves the Pt utilization efficiency after accelerated aging treatments, with encapsulated Pt catalysts reaching reaction rates more than two times greater than those of a control supported Pt catalyst.

  View details for DOI 10.1021/jacs.4c06423

  View details for PubMedID 39137357

• Steam-Assisted Selective CO2 Hydrogenation to Ethanol over Ru-In Catalysts. Angewandte Chemie (International ed. in English) Zhou, C., Aitbekova, A., Liccardo, G., Oh, J., Stone, M., McShane, E. J., Werghi, B., Nathan, S., Song, C., Ciston, J., Bustillo, K., Hoffman, A. S., Hong, J., Perez-Aguilar, J., Bare, S., Cargnello, M. 2024: e202406761

  Abstract

  Multicomponent catalysts can be designed to synergistically combine reaction intermediates at interfacial active sites, but restructuring makes systematic control and understanding of such dynamics challenging. We here unveil how reducibility and mobility of indium oxide species in Ru-based catalysts crucially control the direct, selective conversion of CO2 to ethanol. When uncontrolled, reduced indium oxide species occupy the Ru surface, leading to deactivation. With the addition of steam as a mild oxidant and using porous polymer layers to control In mobility, Ru-In2O3 interface sites are stabilized, and ethanol can be produced with superior overall selectivity (70%, rest CO). Our work highlights how engineering of bifunctional active ensembles enables cooperativity and synergy at tailored interfaces, which unlocks unprecedented performance in heterogeneous catalysts.

  View details for DOI 10.1002/anie.202406761

  View details for PubMedID 38990707

• Understanding and Harnessing Nanoscale Immiscibility in Ru-In Alloys for Selective CO2 Hydrogenation. Journal of the American Chemical Society Zhou, C., Liccardo, G., Hoffman, A. S., Oh, J., Holmes, S. E., Vailionis, A., Bare, S. R., Cargnello, M. 2024

  Abstract

  Bimetallic alloys made from immiscible elements are characterized by their tendency to segregate on the macroscopic scale, but their behavior is known to change at the nanoscale. Here, we demonstrate that in the Ru-In system, In atoms preferentially decorate the surface of 6 nm Ru nanoparticles, forming Ru-In superficial immiscible alloys. This surface decoration dramatically affects the catalytic performance of the system, even at small atomic fractions of In added to Ru. The interfaces between Ru and In enabled unexplored methanol productivity from CO2 hydrogenation, which outperformed not only the individual constituents but also ordered RuIn3 intermetallic alloys. Our work highlights that the formation of superficial immiscible alloys could offer new insights into the understanding and design of heterogeneous catalysts.

  View details for DOI 10.1021/jacs.4c03652

  View details for PubMedID 38985019

• Engineering Ultrathin Alloy Shell in Au@AuPd Core-Shell Nanoparticles for Efficient Plasmon-Driven Photocatalysis ADVANCED MATERIALS INTERFACES Kang, E., Seo, J., Park, H., Wrasman, C. J., Shin, J., Jo, M., Cargnello, M., Park, J., Lee, H. 2024

  View details for DOI 10.1002/admi.202301070

  View details for Web of Science ID 001193972600001

• Palladium Catalysts for Methane Oxidation: Old Materials, New Challenges. Accounts of chemical research Oh, J., Boucly, A., van Bokhoven, J. A., Artiglia, L., Cargnello, M. 2023

  Abstract

  ConspectusMethane complete oxidation is an important reaction that is part of the general scheme used for removing pollutants contained in emissions from internal combustion engines and, more generally, combustion processes. It has also recently attracted interest as an option for the removal of atmospheric methane in the context of negative emission technologies. Methane, a powerful greenhouse gas, can be converted to carbon dioxide and water via its complete oxidation. Despite burning methane being facile because the combustion sustains its complete oxidation after ignition, methane strong C-H bonds require a catalyst to perform the oxidation at low temperatures and in the absence of a flame so as to avoid the formation of nitrogen oxides, such as those produced in flares. This process allows methane removal to be obtained under conditions that usually lead to higher emissions, such as under cold start conditions in the case of internal combustion engines. Among several options that include homo- and heterogeneous catalysts, supported palladium-based catalysts are the most active heterogeneous systems for this reaction. Finely divided palladium can activate C-H bonds at temperatures as low as 150 °C, although complete conversion is usually not reached until 400-500 °C in practical applications. Major goals are to achieve catalytic methane oxidation at as low as possible temperature and to utilize this expensive metal more efficiently.Compared to any other transition metal, palladium and its oxides are orders of magnitude more reactive for methane oxidation in the absence of water. During the last few decades, much research has been devoted to unveiling the origin of the high activity of supported palladium catalysts, their active phase, the effect of support, promoters, and defects, and the effect of reaction conditions with the goal of further improving their reactivity. There is an overall agreement in trends, yet there are noticeable differences in some details of the catalytic performance of palladium, including the active phase under reaction conditions and the reasons for catalyst deactivation and poisoning. In this Account we summarize our work in this space using well-defined catalysts, especially model palladium surfaces and those prepared using colloidal nanocrystals as precursors, and spectroscopic tools to unveil important details about the chemistry of supported palladium catalysts. We describe advanced techniques aimed at elucidating the role of several parameters in the performance of palladium catalysts for methane oxidation as well as in engineering catalysts through advancing fundamental understanding and synthesis methods. We report the state of research on active phases and sites, then move to the role of supports and promoters, and finally discuss stability in catalytic performance and the role of water in the palladium active phase. Overall, we want to emphasize the importance of a fundamental understanding in designing and realizing active and stable palladium-based catalysts for methane oxidation as an example for a variety of energy and environmental applications of nanomaterials in catalysis.

  View details for DOI 10.1021/acs.accounts.3c00454

  View details for PubMedID 38099741

• Technoeconomics and carbon footprint of hydrogen production INTERNATIONAL JOURNAL OF HYDROGEN ENERGY Rojas, J., Zhai, S., Sun, E., Haribal, V., Marin-Quiros, S., Sarkar, A., Gupta, R., Cargnello, M., Chueh, W., Majumdar, A. 2024; 49: 59-74

  View details for DOI 10.1016/j.ijhydene.2023.06.292

  View details for Web of Science ID 001134929300001

• Understanding the effects of manganese and zinc promoters on ferrite catalysts for CO2 hydrogenation to hydrocarbons through colloidal nanocrystals SURFACE SCIENCE Chen, C., Oh, J., Yang, A., Zhou, C., Liccardo, G., Sapru, S., Cargnello, M. 2024; 741

  View details for DOI 10.1016/j.susc.2023.122424

  View details for Web of Science ID 001134321400001

• Ceria Incorporation in Sinter-Resistant Platinum-Based Catalysts ACS CATALYSIS Stone, M. L., Cendejas, M. C., Persson, A., Liccardo, G., Smith, J., Kumar, A., Zhou, C., Gardner, E., Aitbekova, A., Bustillo, K. C., Chi, M., Bare, S. R., Cargnello, M. 2023; 13 (22): 14853-14863

  View details for DOI 10.1021/acscatal.3c02766

  View details for Web of Science ID 001141207100001

• Quantifying Influence of the Solid-Electrolyte Interphase in Ammonia Electrosynthesis ACS ENERGY LETTERS Mcshane, E. J., Niemann, V. A., Benedek, P., Fu, X., Nielander, A. C., Chorkendorff, I., Jaramillo, T. F., Cargnello, M. 2023

  View details for DOI 10.1021/acsenergylett.3c01534

  View details for Web of Science ID 001062617200001

• Activity of Silica-Alumina for the Conversion of Polyethylene into Tunable Aromatics Below Pyrolytic Temperatures ACS SUSTAINABLE CHEMISTRY & ENGINEERING Pennel, M. L., Maurya, A. K., Ebrahim, A. M., Tassone, C. J., Cargnello, M. 2023

  View details for DOI 10.1021/acssuschemeng.3c02295

  View details for Web of Science ID 001050136900001

• A semi-continuous process for co-production of CO2-free hydrogen and carbon nanotubes via methane pyrolysis CELL REPORTS PHYSICAL SCIENCE Sun, E., Zhai, S., Kim, D., Gigantino, M., Haribal, V., Dewey, O. S., Williams, S. M., Wan, G., Nelson, A., Marin-Quiros, S., Martis, J., Zhou, C., Oh, J., Randall, R., Kessler, M., Kong, D., Rojas, J., Tong, A., Xu, X., Huff, C., Pasquali, M., Gupta, R., Cargnello, M., Majumdar, A. 2023; 4 (4)

  View details for DOI 10.1016/j.xcrp.2023.101338

  View details for Web of Science ID 001000123600001

• Selective Catalytic Behavior Induced by Crystal-Phase Transformation in Well-Defined Bimetallic Pt-Sn Nanocrystals. Small (Weinheim an der Bergstrasse, Germany) Werghi, B., Wu, L., Ebrahim, A. M., Chi, M., Ni, H., Cargnello, M., Bare, S. R. 2023: e2207956

  Abstract

  The Pt-Sn bimetallic system is a much studied and commercially used catalyst for propane dehydrogenation. The traditionally prepared catalyst, however, suffers from inhomogeneity and phase separation of the active Pt-Sn phase. Colloidal chemistry offers a route for the synthesis of Pt-Sn bimetallic nanoparticles (NPs) in a systematic, well-defined, tailored fashion over conventional methods. Here, the successful synthesis of well-defined ≈2 nm Pt, PtSn, and Pt3 Sn nanocrystals with distinct crystallographic phases is reported; hexagonal close packing (hcp) PtSn and fcc Pt3 Sn show different activity and stability depending on the hydrogen-rich or poor environment in the feed. Moreover, face centred cubic (fcc) Pt3 Sn/Al2 O3 , which exhibited the highest stability compared to hcp PtSn, shows a unique phase transformation from an fcc phase to an L12 -ordered superlattice. Contrary to PtSn, H2 cofeeding has no effect on the Pt3 Sn deactivation rate. The results reveal structural dependency of the probe reaction, propane dehydrogenation, and provide a fundamental understanding of the structure-performance relationship on emerging bimetallic systems.

  View details for DOI 10.1002/smll.202207956

  View details for PubMedID 36807838

• Studying, Promoting, Exploiting, and Predicting Catalyst Dynamics: the Next Frontier in Heterogeneous Catalysis JOURNAL OF PHYSICAL CHEMISTRY C Chavez, S., Werghi, B., Gutierrez, K., Chen, R., Lall, S., Cargnello, M. 2023

  View details for DOI 10.1021/acs.jpcc.2c065192127J

  View details for Web of Science ID 000929802600001

• Studying, Promoting, Exploiting, and Predicting Catalyst Dynamics: the Next Frontier in Heterogeneous Catalysis JOURNAL OF PHYSICAL CHEMISTRY C Chavez, S., Werghi, B., Gutierrez, K., Chen, R., Lall, S., Cargnello, M. 2023

  View details for DOI 10.1021/acs.jpcc.2c06519

  View details for Web of Science ID 000925348400001

• Colloidally Engineered Pd and Pt Catalysts Distinguish Surface- and Vapor-Mediated Deactivation Mechanisms ACS CATALYSIS Oh, J., Beck, A., Goodman, E. D., Roling, L. T., Boucly, A., Artiglia, L., Abild-Pedersen, F., van Bokhoven, J. A., Cargnello, M. 2023

  View details for DOI 10.1021/acscatal.2c04683

  View details for Web of Science ID 000921989700001

• The mosaic art of interphases NATURE ENERGY McShane, E. J., Cargnello, M. 2023

  View details for DOI 10.1038/s41560-022-01192-6

  View details for Web of Science ID 000914699200001

• A Versatile Li0.5FePO4 Reference Electrode for Nonaqueous Electrochemical Conversion Technologies ACS ENERGY LETTERS McShane, E. J., Benedek, P., Niemann, V. A., Blair, S. J., Kamat, G. A., Nielander, A. C., Jaramillo, T. F., Cargnello, M. 2022: 230-235

  View details for DOI 10.1021/acsenergylett.2c02190

  View details for Web of Science ID 000891330700001

• Templated encapsulation of platinum-based catalysts promotes high-temperature stability to 1,100°C. Nature materials Aitbekova, A., Zhou, C., Stone, M. L., Lezama-Pacheco, J. S., Yang, A., Hoffman, A. S., Goodman, E. D., Huber, P., Stebbins, J. F., Bustillo, K. C., Ercius, P., Ciston, J., Bare, S. R., Plessow, P. N., Cargnello, M. 2022

  Abstract

  Stable catalysts are essential to address energy and environmental challenges, especially for applications in harsh environments (for example, high temperature, oxidizing atmosphere and steam). In such conditions, supported metal catalysts deactivate due to sintering-a process where initially small nanoparticles grow into larger ones with reduced active surface area-but strategies to stabilize them can lead to decreased performance. Here we report stable catalysts prepared through the encapsulation of platinum nanoparticles inside an alumina framework, which was formed by depositing an alumina precursor within a separately prepared porous organic framework impregnated with platinum nanoparticles. These catalysts do not sinter at 800°C in the presence of oxygen and steam, conditions in which conventional catalysts sinter to a large extent, while showing similar reaction rates. Extending this approach to Pd-Pt bimetallic catalysts led to the small particle size being maintained at temperatures as high as 1,100°C in air and 10% steam. This strategy can be broadly applied to other metal and metal oxides for applications where sintering is a major cause of material deactivation.

  View details for DOI 10.1038/s41563-022-01376-1

  View details for PubMedID 36280703

• Recycling of Solvent Allows for Multiple Rounds of Reproducible Nanoparticle Synthesis. Journal of the American Chemical Society Wrasman, C. J., Zhou, C., Aitbekova, A., Goodman, E. D., Cargnello, M. 2022

  Abstract

  Metal nanoparticles have superior properties for a variety of applications. In many cases, the improved performance of metal nanoparticles is tightly correlated with their size and atomic composition. To date, colloidal synthesis is the most commonly used technique to produce metal nanoparticles. However, colloidal synthesis is currently a laboratory scale technique that has not been applied at larger scales. One of the greatest challenges facing large-scale colloidal synthesis of metal nanoparticles is the large volume of long-chain hydrocarbon solvents and surfactants needed for the synthesis, which can dominate the cost of nanoparticle production. In this work, we demonstrate a protocol, based on solvent distillation, which enables the reuse of colloidal nanoparticle synthesis surfactants and solvents for over 10 rounds of successive syntheses and demonstrates that pure solvents and surfactants are not necessarily needed to produce uniform nanocrystals. We show that this protocol can be applied to the production of a wide variety of mono- and bimetallic nanoparticles with reproducible sizes and compositions, which leads to reproducible performance as heterogeneous catalysts. A techno-economic assessment demonstrates the potential of this technique to greatly reduce the solvent-related costs of colloidal metal nanoparticle synthesis, which could contribute to its wider application at commercial scale.

  View details for DOI 10.1021/jacs.2c02837

  View details for PubMedID 35737471

• Steering CO2 hydrogenation toward C-C coupling to hydrocarbons using porous organic polymer/metal interfaces. Proceedings of the National Academy of Sciences of the United States of America Zhou, C., Asundi, A. S., Goodman, E. D., Hong, J., Werghi, B., Hoffman, A. S., Nathan, S. S., Bent, S. F., Bare, S. R., Cargnello, M. 2022; 119 (7)

  Abstract

  The conversion of CO2 into fuels and chemicals is an attractive option for mitigating CO2 emissions. Controlling the selectivity of this process is beneficial to produce desirable liquid fuels, but C-C coupling is a limiting step in the reaction that requires high pressures. Here, we propose a strategy to favor C-C coupling on a supported Ru/TiO2 catalyst by encapsulating it within the polymer layers of an imine-based porous organic polymer that controls its selectivity. Such polymer confinement modifies the CO2 hydrogenation behavior of the Ru surface, significantly enhancing the C2+ production turnover frequency by 10-fold. We demonstrate that the polymer layers affect the adsorption of reactants and intermediates while being stable under the demanding reaction conditions. Our findings highlight the promising opportunity of using polymer/metal interfaces for the rational engineering of active sites and as a general tool for controlling selective transformations in supported catalyst systems.

  View details for DOI 10.1073/pnas.2114768119

  View details for PubMedID 35135880

• Colloidal Platinum-Copper Nanocrystal Alloy Catalysts Surpass Platinum in Low-Temperature Propene Combustion. Journal of the American Chemical Society Tahsini, N., Yang, A. C., Streibel, V., Werghi, B., Goodman, E. D., Aitbekova, A., Bare, S. R., Li, Y., Abild-Pedersen, F., Cargnello, M. 2022

  Abstract

  Low-temperature removal of noxious environmental emissions plays a critical role in minimizing the harmful effects of hydrocarbon fuels. Emission-control catalysts typically consist of large quantities of rare, noble metals (e.g., platinum and palladium), which are expensive and environmentally damaging metals to extract. Alloying with cheaper base metals offers the potential to boost catalytic activity while optimizing the use of noble metals. In this work, we show that PtxCu100-x catalysts prepared from colloidal nanocrystals are more active than the corresponding Pt catalysts for complete propene oxidation. By carefully controlling their composition while maintaining nanocrystal size, alloys with dilute Cu concentrations (15-30% atomic fraction) demonstrate promoted activity compared to pure Pt. Complete propene oxidation was observed at temperatures as low as 150 °C in the presence of steam, and five to ten times higher turnover frequencies were found compared to monometallic Pt catalysts. Through DFT studies and structural and catalytic characterization, the remarkable activity of dilute PtxCu100-x alloys was related to the tuning of the electronic structure of Pt to reach optimal binding energies of C* and O* intermediates. This work provides a general approach toward investigation of structure-property relationships of alloyed catalysts with efficient and optimized use of noble metals.

  View details for DOI 10.1021/jacs.1c10248

  View details for PubMedID 35050603

• Voltage cycling process for the electroconversion of biomass-derived polyols. Proceedings of the National Academy of Sciences of the United States of America Kim, D., Zhou, C., Zhang, M., Cargnello, M. 2021; 118 (41)

  Abstract

  Electrification of chemical reactions is crucial to fundamentally transform our society that is still heavily dependent on fossil resources and unsustainable practices. In addition, electrochemistry-based approaches offer a unique way of catalyzing reactions by the fast and continuous alteration of applied potentials, unlike traditional thermal processes. Here, we show how the continuous cyclic application of electrode potential allows Pt nanoparticles to electrooxidize biomass-derived polyols with turnover frequency improved by orders of magnitude compared with the usual rates at fixed potential conditions. Moreover, secondary alcohol oxidation is enhanced, with a ketoses-to-aldoses ratio increased up to sixfold. The idea has been translated into the construction of a symmetric single-compartment system in a two-electrode configuration. Its operation via voltage cycling demonstrates high-rate sorbitol electrolysis with the formation of H2 as a desired coproduct at operating voltages below 1.4 V. The devised method presents a potential approach to using renewable electricity to drive chemical processes.

  View details for DOI 10.1073/pnas.2113382118

  View details for PubMedID 34615713

• Monolayer Support Control and Precise Colloidal Nanocrystals Demonstrate Metal-Support Interactions in Heterogeneous Catalysts. Advanced materials (Deerfield Beach, Fla.) Goodman, E. D., Asundi, A. S., Hoffman, A. S., Bustillo, K. C., Stebbins, J. F., Bare, S. R., Bent, S. F., Cargnello, M. 2021: e2104533

  Abstract

  Electronic and geometric interactions between active and support phases are critical in determining the activity of heterogeneous catalysts, but metal-support interactions are challenging to study. Here, it is demonstrated how the combination of the monolayer-controlled formation using atomic layer deposition (ALD) and colloidal nanocrystal synthesis methods leads to catalysts with sub-nanometer precision of active and support phases, thus allowing for the study of the metal-support interactions in detail. The use of this approach in developing a fundamental understanding of support effects in Pd-catalyzed methane combustion is demonstrated. Uniform Pd nanocrystals are deposited onto Al2 O3 /SiO2 spherical supports prepared with control over morphology and Al2 O3 layer thicknesses ranging from sub-monolayer to a 4nm thick uniform coating. Dramatic changes in catalytic activity depending on the coverage and structure of Al2 O3 situated at the Pd/Al2 O3 interface are observed, with even a single monolayer of alumina contributing an order of magnitude increase in reaction rate. By building the Pd/Al2 O3 interface up layer-by-layer and using uniform Pd nanocrystals, this work demonstrates the importance of controlled and tunable materials in determining metal-support interactions and catalyst activity.

  View details for DOI 10.1002/adma.202104533

  View details for PubMedID 34535919

• Insights and comparison of structure-property relationships in propane and propene catalytic combustion on Pd- and Pt-based catalysts JOURNAL OF CATALYSIS Yang, A., Streibel, V., Choksi, T. S., Aljama, H., Werghi, B., Bare, S. R., Sanchez-Carrera, R. S., Schaefer, A., Li, Y., Abild-Pedersen, F., Cargnello, M. 2021; 401: 89-101

  View details for DOI 10.1016/j.jcat.2021.06.018

  View details for Web of Science ID 000691545800010

• Support Acidity Improves Pt Activity in Propane Combustion in the Presence of Steam by Reducing Water Coverage on the Active Sites ACS CATALYSIS Yang, A., Zhu, H., Li, Y., Cargnello, M. 2021; 11 (11): 6672-6683

  View details for DOI 10.1021/acscatal.1c01280

  View details for Web of Science ID 000661125100034

• A General Approach for Monolayer Adsorption of High Weight Loadings of Uniform Nanocrystals on Oxide Supports. Angewandte Chemie (International ed. in English) Kao, K., Yang, A., Huang, W., Zhou, C., Goodman, E. D., Holm, A., Frank, C. W., Cargnello, M. 2021

  Abstract

  Monodispersed metal and semiconductor nanocrystals have attracted great attention in fundamental and applied research due to their tunable size, morphology, and well-defined chemical composition. Utilizing these nanocrystals in a controllable way is highly desirable especially when using them as building blocks for the preparation of nanostructured materials. Their deposition onto oxide materials provide them with wide applicability in many areas, including catalysis. However, so far deposition methods are limited and do not provide control to achieve high particle loadings. This study demonstrates a general approach for the deposition of hydrophobic ligand-stabilized nanocrystals on hydrophilic oxide supports without ligand-exchange. Surface functionalization of the supports with primary amine groups either using an organosilane ((3-aminopropyl)trimethoxysilane) or bonding with aminoalcohols (3-amino-1,2-propanediol) were found to significantly improve the interaction between nanocrystals and supports achieving high loadings (>10 wt. %). The bonding method with aminoalcohols guarantees the opportunity to remove the binding molecules thus allowing clean metal/oxide materials to be obtained, which is of great importance in the preparation of supported nanocrystals for heterogeneous catalysis.

  View details for DOI 10.1002/anie.202017238

  View details for PubMedID 33403788

• Steam-created grain boundaries for methane C-H activation in palladium catalysts. Science (New York, N.Y.) Huang, W., Johnston-Peck, A. C., Wolter, T., Yang, W. D., Xu, L., Oh, J., Reeves, B. A., Zhou, C., Holtz, M. E., Herzing, A. A., Lindenberg, A. M., Mavrikakis, M., Cargnello, M. 2021; 373 (6562): 1518-1523

  Abstract

  [Figure: see text].

  View details for DOI 10.1126/science.abj5291

  View details for PubMedID 34554810

• Atmospheric Methane Removal: A Research Agenda Philosophical Transactions of the Royal Society A Jackson, R. B., et al 2021; 379: 20200454

  View details for DOI 10.1098/rsta.2020.0454

• Size-controlled nanocrystals reveal spatial dependence and severity of nanoparticle coalescence and Ostwald ripening in sintering phenomena. Nanoscale Goodman, E. D., Carlson, E. Z., Dietze, E. M., Tahsini, N., Johnson, A., Aitbekova, A., Nguyen Taylor, T., Plessow, P. N., Cargnello, M. 2020

  Abstract

  A major aim in the synthesis of nanomaterials is the development of stable materials for high-temperature applications. Although the thermal coarsening of small and active nanocrystals into less active aggregates is universal in material deactivation, the atomic mechanisms governing nanocrystal growth remain elusive. By utilizing colloidally synthesized Pd/SiO2 powder nanocomposites with controlled nanocrystal sizes and spatial arrangements, we unravel the competing contributions of particle coalescence and atomic ripening processes in nanocrystal growth. Through the study of size-controlled nanocrystals, we can uniquely identify the presence of either nanocrystal dimers or smaller nanoclusters, which indicate the relative contributions of these two processes. By controlling and tracking the nanocrystal density, we demonstrate the spatial dependence of nanocrystal coalescence and the spatial independence of Ostwald (atomic) ripening. Overall, we prove that the most significant loss of the nanocrystal surface area is due to high-temperature atomic ripening. This observation is in quantitative agreement with changes in the nanocrystal density produced by simulations of atomic exchange. Using well-defined colloidal materials, we extend our analysis to explain the unusual high-temperature stability of Au/SiO2 materials up to 800 °C.

  View details for DOI 10.1039/d0nr07960j

  View details for PubMedID 33367382

• A phytophotonic approach to enhanced photosynthesis ENERGY & ENVIRONMENTAL SCIENCE Kunz, L. Y., Redekop, P., Ort, D. R., Grossman, A. R., Cargnello, M., Majumdar, A. 2020; 13 (12): 4794–4807

  View details for DOI 10.1039/d0ee02960b

  View details for Web of Science ID 000599751100013

• Nanoscale Spatial Distribution of Supported Nanoparticles Controls Activity and Stability in Powder Catalysts for CO Oxidation and Photocatalytic H2 Evolution. Journal of the American Chemical Society Holm, A., Goodman, E. D., Stenlid, J. H., Aitbekova, A., Zelaya, R., Diroll, B. T., Johnston-Peck, A. C., Kao, K. C., Frank, C. W., Pettersson, L. G., Cargnello, M. 2020; 142 (34): 14481-14494

  Abstract

  Supported metal nanoparticles are essential components of high-performing catalysts, and their structures are intensely researched. In comparison, nanoparticle spatial distribution in powder catalysts is conventionally not quantified, and the influence of this collective property on catalyst performance remains poorly investigated. Here, we demonstrate a general colloidal self-assembly method to control uniformity of nanoparticle spatial distribution on common industrial powder supports. We quantify distributions on the nanoscale using image statistics and show that the type of nanospatial distribution determines not only the stability, but also the activity of heterogeneous catalysts. Widely investigated systems (Au-TiO2 for CO oxidation thermocatalysis and Pd-TiO2 for H2 evolution photocatalysis) were used to showcase the universal importance of nanoparticle spatial organization. Spatially and temporally resolved microkinetic modeling revealed that nonuniformly distributed Au nanoparticles suffer from local depletion of surface oxygen, and therefore lower CO oxidation activity, as compared to uniformly distributed nanoparticles. Nanoparticle spatial distribution also determines the stability of Pd-TiO2 photocatalysts, because nonuniformly distributed nanoparticles sinter while uniformly distributed nanoparticles do not. This work introduces new tools to evaluate and understand catalyst collective (ensemble) properties in powder catalysts, which thereby pave the way to more active and stable heterogeneous catalysts.

  View details for DOI 10.1021/jacs.0c03842

  View details for PubMedID 32786792

• Dynamics of Copper-Containing Porous Organic Framework Catalysts Reveal Catalytic Behavior Controlled by the Polymer Structure ACS CATALYSIS Wu, Z., Zhang, X., Goodman, E. D., Huang, W., Riscoe, A. R., Yacob, S., Cargnello, M. 2020; 10 (16): 9356–65

  View details for DOI 10.1021/acscatal.0c01863

  View details for Web of Science ID 000563749900031

• Enhanced Catalytic Activity for Methane Combustion through in Situ Water Sorption ACS CATALYSIS Huang, W., Zhang, X., Yang, A., Goodman, E. D., Kao, K., Cargnello, M. 2020; 10 (15): 8157–67

  View details for DOI 10.1021/acscatal.0c02087

  View details for Web of Science ID 000562075000013

• Chemically Controllable Porous Polymer-Nanocrystal Composites with Hierarchical Arrangement Show Substrate Transport Selectivity CHEMISTRY OF MATERIALS Riscoe, A. R., Wrasman, C. J., Menon, A., Dinakar, B., Goodman, E. D., Kunz, L. Y., Yacob, S., Cargnello, M. 2020; 32 (13): 5904–15

  View details for DOI 10.1021/acs.chemmater.0c02233

  View details for Web of Science ID 000551412800051

• Formic acid oxidation boosted by Rh single atoms. Nature nanotechnology Kim, D., Cargnello, M. 2020

  View details for DOI 10.1038/s41565-020-0659-8

  View details for PubMedID 32231269

• Dilute Pd/Au Alloys Replace Au/TiO2 Interface for Selective Oxidation Reactions ACS CATALYSIS Wrasman, C. J., Riscoe, A. R., Lee, H., Cargnello, M. 2020; 10 (3): 1716–20

  View details for DOI 10.1021/acscatal.9b05227

  View details for Web of Science ID 000513099200006

• A Combined Theory-Experiment Analysis of the Surface Species in Lithium-Mediated NH3 Electrosynthesis CHEMELECTROCHEM Schwalbe, J. A., Statt, M. J., Chosy, C., Singh, A. R., Rohr, B. A., Nielander, A. C., Andersen, S. Z., McEnaney, J. M., Baker, J. G., Jaramillo, T. F., Norskov, J. K., Cargnello, M. 2020

  View details for DOI 10.1002/celc.201902124

  View details for Web of Science ID 000510258500001

• Design of Organic/Inorganic Hybrid Catalysts for Energy and Environmental Applications. ACS central science Goodman, E. D., Zhou, C. n., Cargnello, M. n. 2020; 6 (11): 1916–37

  Abstract

  Controlling selectivity between competing reaction pathways is crucial in catalysis. Several approaches have been proposed to achieve this goal in traditional heterogeneous catalysts including tuning nanoparticle size, varying alloy composition, and controlling supporting material. A less explored and promising research area to control reaction selectivity is via the use of hybrid organic/inorganic catalysts. These materials contain inorganic components which serve as sites for chemical reactions and organic components which either provide diffusional control or directly participate in the formation of active site motifs. Despite the appealing potential of these hybrid materials to increase reaction selectivity, there are significant challenges to the rational design of such hybrid nanostructures. Structural and mechanistic characterization of these materials play a key role in understanding and, therefore, designing these organic/inorganic hybrid catalysts. This Outlook highlights the design of hybrid organic/inorganic catalysts with a brief overview of four different classes of materials and discusses the practical catalytic properties and opportunities emerging from such designs in the area of energy and environmental transformations. Key structural and mechanistic characterization studies are identified to provide fundamental insight into the atomic structure and catalytic behavior of hybrid organic/inorganic catalysts. Exemplary works are used to show how specific active site motifs allow for remarkable changes in the reaction selectivity. Finally, to demonstrate the potential of hybrid catalyst materials, we suggest a characterization-based approach toward the design of biomimetic hybrid organic/inorganic materials for a specific application in the energy and environmental research space: the conversion of methane into methanol.

  View details for DOI 10.1021/acscentsci.0c01046

  View details for PubMedID 33274270

  View details for PubMedCentralID PMC7706093

• Revealing the structure of a catalytic combustion active-site ensemble combining uniform nanocrystal catalysts and theory insights. Proceedings of the National Academy of Sciences of the United States of America Yang, A. C., Choksi, T. n., Streibel, V. n., Aljama, H. n., Wrasman, C. J., Roling, L. T., Goodman, E. D., Thomas, D. n., Bare, S. R., Sánchez-Carrera, R. S., Schäfer, A. n., Li, Y. n., Abild-Pedersen, F. n., Cargnello, M. n. 2020

  Abstract

  Supported metal catalysts are extensively used in industrial and environmental applications. To improve their performance, it is crucial to identify the most active sites. This identification is, however, made challenging by the presence of a large number of potential surface structures that complicate such an assignment. Often, the active site is formed by an ensemble of atoms, thus introducing further complications in its identification. Being able to produce uniform structures and identify the ones that are responsible for the catalyst performance is a crucial goal. In this work, we utilize a combination of uniform Pd/Pt nanocrystal catalysts and theory to reveal the catalytic active-site ensemble in highly active propene combustion materials. Using colloidal chemistry to exquisitely control nanoparticle size, we find that intrinsic rates for propene combustion in the presence of water increase monotonically with particle size on Pt-rich catalysts, suggesting that the reaction is structure dependent. We also reveal that water has a near-zero or mildly positive reaction rate order over Pd/Pt catalysts. Theory insights allow us to determine that the interaction of water with extended terraces present in large particles leads to the formation of step sites on metallic surfaces. These specific step-edge sites are responsible for the efficient combustion of propene at low temperature. This work reveals an elusive geometric ensemble, thus clearly identifying the active site in alkene combustion catalysts. These insights demonstrate how the combination of uniform catalysts and theory can provide a much deeper understanding of active-site geometry for many applications.

  View details for DOI 10.1073/pnas.2002342117

  View details for PubMedID 32554500

• Transition state and product diffusion control by polymer-nanocrystal hybrid catalysts NATURE CATALYSIS Riscoe, A. R., Wrasman, C. J., Herzing, A. A., Hoffman, A. S., Menon, A., Boubnov, A., Vargas, M., Bare, S. R., Cargnello, M. 2019; 2 (10): 852–63

  View details for DOI 10.1038/s41929-019-0322-7

  View details for Web of Science ID 000489769600009

• Engineering of Ruthenium-Iron Oxide Colloidal Heterostructures Leads to Improved Yields in CO2 Hydrogenation to Hydrocarbons. Angewandte Chemie (International ed. in English) Cargnello, M., Aitbekova, A., Goodman, E., Wu, L., Boubnov, A., Hoffman, A., Genc, A., Cheng, H., Casalena, L., Bare, S. 2019

  Abstract

  Catalytic CO2 reduction to fuels and chemicals is one of the major pursuits in reducing greenhouse gas emissions. One such popular approach utilizes the reverse water-gas shift reaction, followed by Fischer-Tropsch synthesis, and iron is a well-known candidate for this process. Some attempts have been made to modify and improve its reactivity, but resuted in limited success. In this work, using ruthenium-iron oxide colloidal heterodimers we demonstrate that close contact between the two phases promotes the reduction of iron oxide via a proximal hydrogen spillover effect, leading to the formation of ruthenium-iron core-shell structures active for the reaction at significantly lower temperatures than in bare iron catalysts. Furthermore, by engineering the iron oxide shell thickness, we achieve a fourfold increase in hydrocarbon yield compared to the heterodimers. In general, our work shows how rational design of colloidal heterostructures can result in materials with significantly improved catalytic performance in CO2 conversion processes.

  View details for DOI 10.1002/anie.201910579

  View details for PubMedID 31545533

• Catalyst deactivation via decomposition into single atoms and the role of metal loading NATURE CATALYSIS Goodman, E. D., Johnston-Peck, A. C., Dietze, E. M., Wrasman, C. J., Hoffman, A. S., Abild-Pedersen, F., Bare, S. R., Plessow, P. N., Cargnello, M. 2019; 2 (9): 748–55

  View details for DOI 10.1038/s41929-019-0328-1

  View details for Web of Science ID 000486144700006

• A Versatile Method for Ammonia Detection in a Range of Relevant Electrolytes via Direct Nuclear Magnetic Resonance Techniques ACS CATALYSIS Nielander, A. C., McEnaney, J. M., Schwalbe, J. A., Baker, J. G., Blair, S. J., Wang, L., Pelton, J. G., Andersen, S. Z., Enemark-Rasmussen, K., Colic, V., Yang, S., Bent, S. F., Cargnello, M., Kibsgaard, J., Vesborg, P. K., Chorkendorff, I., Jaramillo, T. F. 2019; 9 (7): 5797–5802

  View details for DOI 10.1021/acscatal.9b00358

  View details for Web of Science ID 000474812400001

• A rigorous electrochemical ammonia synthesis protocol with quantitative isotope measurements. Nature Andersen, S. Z., Colic, V., Yang, S., Schwalbe, J. A., Nielander, A. C., McEnaney, J. M., Enemark-Rasmussen, K., Baker, J. G., Singh, A. R., Rohr, B. A., Statt, M. J., Blair, S. J., Mezzavilla, S., Kibsgaard, J., Vesborg, P. C., Cargnello, M., Bent, S. F., Jaramillo, T. F., Stephens, I. E., Norskov, J. K., Chorkendorff, I. 2019

  Abstract

  The electrochemical synthesis of ammonia from nitrogen under mild conditions and using renewable electricity is in principle an attractive alternative1-4 to the demanding, energy-intense Haber-Bosch process, which dominates industrial ammonia production. However, the electrochemical alternative faces considerable scientific and technical challenges5,6 and most experimental studies reported thus far achieve only low selectivities and conversions. In fact, the amount of ammonia produced is usually so small that it is difficult to firmly attribute it to electrochemical nitrogen fixation7-9 and exclude contamination due to ammonia that is either present in air, human breath or ion-conducting membranes9, or generated from labile nitrogen-containing compounds (for example, nitrates, amines, nitrites and nitrogen oxides) that are typically present in the nitrogen gas stream10, in the atmosphere or even the catalyst itself. Although these many and varied sources of potential experimental artefacts are beginning to be recognized and dealt with11,12, concerted efforts to develop effective electrochemical nitrogen reduction processes would benefit from benchmarking protocols for the reaction and from a standardized set of control experiments to identify and then eliminate or quantify contamination sources. Here we put forward such a rigorous procedure that, by making essential use of 15N2, allows us to reliably detect and quantify the electroreduction of N2 to NH3. We demonstrate experimentally the significance of various sources of contamination and show how to remove labile nitrogen-containing compounds present in the N2 gas and how to perform quantitative isotope measurements with cycling of 15N2 gas to reduce both contamination and the cost of isotope measurements. Following this protocol, we obtain negative results when using the most promising pure metal catalysts in aqueous media, and successfully confirm and quantify ammonia synthesis using lithium electrodeposition in tetrahydrofuran13.

  View details for DOI 10.1038/s41586-019-1260-x

  View details for PubMedID 31117118

• Artificial inflation of apparent photocatalytic activity induced by catalyst-mass-normalization and a method to fairly compare heterojunction systems ENERGY & ENVIRONMENTAL SCIENCE Kunz, L. Y., Diroll, B. T., Wrasman, C. J., Riscoe, A. R., Majumdar, A., Cargnello, M. 2019; 12 (5): 1657–67

  View details for DOI 10.1039/c9ee00452a

  View details for Web of Science ID 000473083100015

• Colloidal Nanocrystals as Building Blocks for Well-Defined Heterogeneous Catalysts CHEMISTRY OF MATERIALS Cargnello, M. 2019; 31 (3): 576–96

  View details for DOI 10.1021/acs.chemmater.8b04533

  View details for Web of Science ID 000458937800003

• Colloidal nanocrystals for heterogeneous catalysis NANO TODAY Losch, P., Huang, W., Goodman, E. D., Wrasman, C. J., Holm, A., Riscoe, A. R., Schwalbe, J. A., Cargnello, M. 2019; 24: 15–47

  View details for DOI 10.1016/j.nantod.2018.12.002

  View details for Web of Science ID 000460817600007

• Supported Catalyst Deactivation by Decomposition into Single Atoms Is Suppressed by Increasing Metal Loading. Nature catalysis Goodman, E. D., Johnston-Peck, A. C., Dietze, E. M., Wrasman, C. J., Hoffman, A. S., Abild-Pedersen, F., Bare, S. R., Plessow, P. N., Cargnello, M. 2019; 2

  Abstract

  In the high-temperature environments needed to perform catalytic processes, supported precious metal catalysts severely lose their activity over time. Even brief exposure to high temperatures can lead to significant losses in activity, which forces manufacturers to use large amounts of noble metals to ensure effective catalyst function for a required lifetime. Generally, loss of catalytic activity is attributed to nanoparticle sintering, or processes by which larger particles grow at the expense of smaller ones. Here, by independently controlling particle size and particle loading using colloidal nanocrystals, we reveal the opposite process as a novel deactivation mechanism: nanoparticles rapidly lose activity by high-temperature nanoparticle decomposition into inactive single atoms. This deactivation route is remarkably fast, leading to severe loss of activity in as little as ten minutes. Importantly, this deactivation pathway is strongly dependent on particle density and concentration of support defect sites. A quantitative statistical model explains how for certain reactions, higher particle densities can lead to more stable catalysts.

  View details for DOI 10.1038/s41929-019-0328-1

  View details for PubMedID 32118197

  View details for PubMedCentralID PMC7047889

• Synthesis of Colloidal Pd/Au Dilute Alloy Nanocrystals and Their Potential for Selective Catalytic Oxidations. Journal of the American Chemical Society Wrasman, C. J., Boubnov, A., Riscoe, A. R., Hoffman, A. S., Bare, S. R., Cargnello, M. 2018

  Abstract

  Selective oxidations are crucial for the creation of valuable chemical building blocks but often require expensive and unstable stoichiometric oxidants such as hydroperoxides and peracids. To date, many catalysts that contain a single type of active site have not been able to attain the desired level of selectivity for partially oxidized products over total combustion. However, catalysts containing multiple types of active sites have proven to be successful for selective reactions. One category of such catalysts is bimetallic alloys, in which catalytic activity and selectivity can be tuned by modifying the surface composition. Traditional catalyst synthesis methods using impregnation struggle to create catalysts with sufficient control over surface chemistry to accurately tune the ensemble size of the desired active sites. Here we describe the synthesis of colloidal nanocrystals of dilute alloys of palladium and gold. We show that when supported on titania (TiO2), tuning the composition of the Pd/Au nanocrystal surface provides a synergistic effect in the selective oxidation of 2-propanol to acetone in the presence of H2 and O2. In particular, we show that certain Pd/Au surface ratios exhibit activity and selectivity far superior to Pd or Au individually. Through precise structural characterization we demonstrate that isolated atoms of Pd exist in the most active catalysts. The synergy between isolated Pd atoms and Au allows for the formation of reactive oxidizing species, likely hydroperoxide groups, responsible for selective oxidation while limiting oxygen dissociation and, thus, complete combustion. This work opens the way to more efficient utilization of scarce noble metals and new options for catalyzed selective oxidations.

  View details for PubMedID 30220200

• Deconvoluting Transient Water Effects on the Activity of Pd Methane Combustion Catalysts INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH Huang, W., Goodman, E. D., Losch, P., Cargnello, M. 2018; 57 (31): 10261–68

  View details for DOI 10.1021/acs.iecr.8b01915

  View details for Web of Science ID 000441475700021

• In Situ X-ray Scattering Guides the Synthesis of Uniform PtSn Nanocrystals. Nano letters Wu, L., Fournier, A. P., Willis, J. J., Cargnello, M., Tassone, C. J. 2018

  Abstract

  Compared to monometallic nanocrystals (NCs), bimetallic ones often exhibit superior properties due to their wide tunability in structure and composition. A detailed understanding of their synthesis at the atomic scale provides crucial knowledge for their rational design. Here, exploring the Pt-Sn bimetallic system as an example, we study in detail the synthesis of PtSn NCs using in situ synchrotron X-ray scattering. We show that when Pt(II) and Sn(IV) precursors are used, in contrast to a typical simultaneous reduction mechanism, the PtSn NCs are formed through an initial reduction of Pt(II) to form Pt NCs, followed by the chemical transformation from Pt to PtSn. The kinetics derived from the in situ measurements shows fast diffusion of Sn into the Pt lattice accompanied by reordering of these atoms into intermetallic PtSn structure within 300 s at the reaction temperature (280 °C). This crucial mechanistic understanding enables the synthesis of well-defined PtSn NCs with controlled structure and composition via a seed-mediated approach. This type of in situ characterization can be extended to other multicomponent nanostructures to advance their rational synthesis for practical applications.

  View details for PubMedID 29812947

• Low-Temperature Restructuring of CeO2-Supported Ru Nanoparticles Determines Selectivity in CO2 Catalytic Reduction. Journal of the American Chemical Society Aitbekova, A. n., Wu, L. n., Wrasman, C. J., Boubnov, A. n., Hoffman, A. S., Goodman, E. D., Bare, S. R., Cargnello, M. n. 2018; 140 (42): 13736–45

  Abstract

  CO2 reduction to higher value products is a promising way to produce fuels and key chemical building blocks while reducing CO2 emissions. The reaction at atmospheric pressure mainly yields CH4 via methanation and CO via the reverse water-gas shift (RWGS) reaction. Describing catalyst features that control the selectivity of these two pathways is important to determine the formation of specific products. At the same time, identification of morphological changes occurring to catalysts under reaction conditions can be crucial to tune their catalytic performance. In this contribution we investigate the dependency of selectivity for CO2 reduction on the size of Ru nanoparticles (NPs) and on support. We find that even at rather low temperatures (210 °C), oxidative pretreatment induces redispersion of Ru NPs supported on CeO2 and leads to a complete switch in the performance of this material from a well-known selective methanation catalyst to an active and selective RWGS catalyst. By utilizing in situ X-ray absorption spectroscopy, we demonstrate that the low-temperature redispersion process occurs via decomposition of the metal oxide phase with size-dependent kinetics, producing stable single-site RuO x/CeO2 species strongly bound to the CeO2 support that are remarkably selective for CO production. These results show that reaction selectivity can be heavily dependent on catalyst structure and that structural changes of the catalyst can occur even at low temperatures and can go unseen in materials with less defined structures.

  View details for PubMedID 30252458

• Systematic Identification of Promoters for Methane Oxidation Catalysts Using Size- and Composition-Controlled Pd-Based Bimetallic Nanocrystals. Journal of the American Chemical Society Willis, J. J., Goodman, E. D., Wu, L., Riscoe, A. R., Martins, P., Tassone, C. J., Cargnello, M. 2017; 139 (34): 11989-11997

  Abstract

  Promoters enhance the performance of catalytic active phases by increasing rates, stability, and/or selectivity. The process of identifying promoters is in most cases empirical and relies on testing a broad range of catalysts prepared with the random deposition of active and promoter phases, typically with no fine control over their localization. This issue is particularly relevant in supported bimetallic systems, where two metals are codeposited onto high-surface area materials. We here report the use of colloidal bimetallic nanocrystals to produce catalysts where the active and promoter phases are colocalized to a fine extent. This strategy enables a systematic approach to study the promotional effects of several transition metals on palladium catalysts for methane oxidation. In order to achieve these goals, we demonstrate a single synthetic protocol to obtain uniform palladium-based bimetallic nanocrystals (PdM, M = V, Mn, Fe, Co, Ni, Zn, Sn, and potentially extendable to other metal combinations) with a wide variety of compositions and sizes based on high-temperature thermal decomposition of readily available precursors. Once the nanocrystals are supported onto oxide materials, thermal treatments in air cause segregation of the base metal oxide phase in close proximity to the Pd phase. We demonstrate that some metals (Fe, Co, and Sn) inhibit the sintering of the active Pd metal phase, while others (Ni and Zn) increase its intrinsic activity compared to a monometallic Pd catalyst. This procedure can be generalized to systematically investigate the promotional effects of metal and metal oxide phases for a variety of active metal-promoter combinations and catalytic reactions.

  View details for DOI 10.1021/jacs.7b06260

  View details for PubMedID 28800226

• High-temperature crystallization of nanocrystals into three-dimensional superlattices NATURE Wu, L., Willis, J. J., McKay, I., Diroll, B. T., Qin, J., Cargnello, M., Tassone, C. J. 2017; 548 (7666): 197-+

  Abstract

  Crystallization of colloidal nanocrystals into superlattices represents a practical bottom-up process with which to create ordered metamaterials with emergent functionalities. With precise control over the size, shape and composition of individual nanocrystals, various single- and multi-component nanocrystal superlattices have been produced, the lattice structures and chemical compositions of which can be accurately engineered. Nanocrystal superlattices are typically prepared by carefully controlling the assembly process through solvent evaporation or destabilization or through DNA-guided crystallization. Slow solvent evaporation or cooling of nanocrystal solutions (over hours or days) is the key element for successful crystallization processes. Here we report the rapid growth (seconds) of micrometre-sized, face-centred-cubic, three-dimensional nanocrystal superlattices during colloidal synthesis at high temperatures (more than 230 degrees Celsius). Using in situ small-angle X-ray scattering, we observe continuous growth of individual nanocrystals within the lattices, which results in simultaneous lattice expansion and fine nanocrystal size control due to the superlattice templates. Thermodynamic models demonstrate that balanced attractive and repulsive interparticle interactions dictated by the ligand coverage on nanocrystal surfaces and nanocrystal core size are responsible for the crystallization process. The interparticle interactions can also be controlled to form different superlattice structures, such as hexagonal close-packed lattices. The rational assembly of various nanocrystal systems into novel materials is thus facilitated for both fundamental research and for practical applications in the fields of magnetics, electronics and catalysis.

  View details for PubMedID 28759888

• Elucidating the synergistic mechanism of nickel-molybdenum electrocatalysts for the hydrogen evolution reaction MRS COMMUNICATIONS Mckay, I. S., Schwalbe, J. A., Goodman, E. D., Willis, J. J., Majumdar, A., Cargnello, M. 2016; 6 (3): 241-246

  View details for DOI 10.1557/mrc.2016.27

  View details for Web of Science ID 000389137400013

• Polycatenar Ligand Control of the Synthesis and Self-Assembly of Colloidal Nanocrystals JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Diroll, B. T., Jishkariani, D., Cargnello, M., Murray, C. B., Donnio, B. 2016; 138 (33): 10508-10515

  Abstract

  Hydrophobic colloidal nanocrystals are typically synthesized and manipulated with commercially available ligands, and surface functionalization is therefore typically limited to a small number of molecules. Here, we report the use of polycatenar ligands derived from polyalkylbenzoates for the direct synthesis of metallic, chalcogenide, pnictide, and oxide nanocrystals. Polycatenar molecules, branched structures bearing diverging chains in which the terminal substitution pattern, functionality, and binding group can be independently modified, offer a modular platform for the development of ligands with targeted properties. Not only are these ligands used for the direct synthesis of monodisperse nanocrystals, but nanocrystals coated with polycatenar ligands self-assemble into softer bcc superlattices that deviate from conventional harder close-packed structures (fcc or hcp) formed by the same nanocrystals coated with commercial ligands. Self-assembly experiments demonstrate that the molecular structure of polycatenar ligands encodes interparticle spacings and attractions, engineering self-assembly, which is tunable from hard sphere to soft sphere behavior.

  View details for DOI 10.1021/jacs.6b04979

  View details for Web of Science ID 000382181900025

  View details for PubMedID 27472457

• Revealing particle growth mechanisms by combining high-surface-area catalysts made with monodisperse particles and electron microscopy conducted at atmospheric pressure JOURNAL OF CATALYSIS Zhang, S., Cargnello, M., Cai, W., Murray, C. B., Graham, G. W., Pan, X. 2016; 337: 240-247

  View details for DOI 10.1016/j.jcat.2016.02.020

  View details for Web of Science ID 000374920400026

• Engineering titania nanostructure to tune and improve its photocatalytic activity PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Cargnello, M., Montini, T., Smolin, S. Y., Priebe, J. B., Jaen, J. J., Doan-Nguyen, V. V., Mckay, I. S., Schwalbe, J. A., Pohl, M., Gordon, T. R., Lu, Y., Baxter, J. B., Brueckner, A., Fornasiero, P., Murray, C. B. 2016; 113 (15): 3966-3971

  Abstract

  Photocatalytic pathways could prove crucial to the sustainable production of fuels and chemicals required for a carbon-neutral society. Electron-hole recombination is a critical problem that has, so far, limited the efficiency of the most promising photocatalytic materials. Here, we show the efficacy of anisotropy in improving charge separation and thereby boosting the activity of a titania (TiO2) photocatalytic system. Specifically, we show that H2 production in uniform, one-dimensional brookite titania nanorods is highly enhanced by engineering their length. By using complimentary characterization techniques to separately probe excited electrons and holes, we link the high observed reaction rates to the anisotropic structure, which favors efficient carrier utilization. Quantum yield values for hydrogen production from ethanol, glycerol, and glucose as high as 65%, 35%, and 6%, respectively, demonstrate the promise and generality of this approach for improving the photoactivity of semiconducting nanostructures for a wide range of reacting systems.

  View details for DOI 10.1073/pnas.1524806113

  View details for Web of Science ID 000373762400034

  View details for PubMedID 27035977

  View details for PubMedCentralID PMC4839447

• Substitutional doping in nanocrystal superlattices NATURE Cargnello, M., Johnston-Peck, A. C., Diroll, B. T., Wong, E., Datta, B., Damodhar, D., Doan-Nguyen, V. V., Herzing, A. A., Kagan, C. R., Murray, C. B. 2015; 524 (7566): 450-?

  View details for DOI 10.1038/nature14872

  View details for Web of Science ID 000360069300034

• Substitutional doping in nanocrystal superlattices. Nature Cargnello, M., Johnston-Peck, A. C., Diroll, B. T., Wong, E., Datta, B., Damodhar, D., Doan-Nguyen, V. V., Herzing, A. A., Kagan, C. R., Murray, C. B. 2015; 524 (7566): 450-3

  Abstract

  Doping is a process in which atomic impurities are intentionally added to a host material to modify its properties. It has had a revolutionary impact in altering or introducing electronic, magnetic, luminescent, and catalytic properties for several applications, for example in semiconductors. Here we explore and demonstrate the extension of the concept of substitutional atomic doping to nanometre-scale crystal doping, in which one nanocrystal is used to replace another to form doped self-assembled superlattices. Towards this goal, we show that gold nanocrystals act as substitutional dopants in superlattices of cadmium selenide or lead selenide nanocrystals when the size of the gold nanocrystal is very close to that of the host. The gold nanocrystals occupy random positions in the superlattice and their density is readily and widely controllable, analogous to the case of atomic doping, but here through nanocrystal self-assembly. We also show that the electronic properties of the superlattices are highly tunable and strongly affected by the presence and density of the gold nanocrystal dopants. The conductivity of lead selenide films, for example, can be manipulated over at least six orders of magnitude by the addition of gold nanocrystals and is explained by a percolation model. As this process relies on the self-assembly of uniform nanocrystals, it can be generally applied to assemble a wide variety of nanocrystal-doped structures for electronic, optical, magnetic, and catalytic materials.

  View details for DOI 10.1038/nature14872

  View details for PubMedID 26310766

• Efficient Removal of Organic Ligands from Supported Nanocrystals by Fast Thermal Annealing Enables Catalytic Studies on Well-Defined Active Phases JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Cargnello, M., Chen, C., Diroll, B. T., Doan-Nguyen, V. V., Gorte, R. J., Murray, C. B. 2015; 137 (21): 6906-6911

  Abstract

  A simple yet efficient method to remove organic ligands from supported nanocrystals is reported for activating uniform catalysts prepared by colloidal synthesis procedures. The method relies on a fast thermal treatment in which ligands are quickly removed in air, before sintering can cause changes in the size and shape of the supported nanocrystals. A short treatment at high temperatures is found to be sufficient for activating the systems for catalytic reactions. We show that this method is widely applicable to nanostructures of different sizes, shapes, and compositions. Being rapid and effective, this procedure allows the production of monodisperse heterogeneous catalysts for studying a variety of structure-activity relationships. We show here results on methane steam reforming, where the particle size controls the CO/CO2 ratio on alumina-supported Pd, demonstrating the potential applications of the method in catalysis.

  View details for DOI 10.1021/jacs.5b03333

  View details for Web of Science ID 000355890600025

  View details for PubMedID 25961673

• Dynamic structural evolution of supported palladium-ceria core-shell catalysts revealed by in situ electron microscopy. Nature communications Zhang, S., Chen, C., Cargnello, M., Fornasiero, P., Gorte, R. J., Graham, G. W., Pan, X. 2015; 6: 7778-?

  Abstract

  The exceptional activity for methane combustion of modular palladium-ceria core-shell subunits on silicon-functionalized alumina that was recently reported has created renewed interest in the potential of core-shell structures as catalysts. Here we report on our use of advanced ex situ and in situ electron microscopy with atomic resolution to show that the modular palladium-ceria core-shell subunits undergo structural evolution over a wide temperature range. In situ observations performed in an atmospheric gas cell within this temperature range provide real-time evidence that the palladium and ceria nanoparticle constituents of the palladium-ceria core-shell participate in a dynamical process that leads to the formation of an unanticipated structure comprised of an intimate mixture of palladium, cerium, silicon and oxygen, with very high dispersion. This finding may open new perspectives about the origin of the activity of this catalyst.

  View details for DOI 10.1038/ncomms8778

  View details for PubMedID 26160065

  View details for PubMedCentralID PMC4510970

• Solution-Phase Synthesis of Titanium Dioxide Nanoparticles and Nanocrystals CHEMICAL REVIEWS Cargnello, M., Gordon, T. R., Murray, C. B. 2014; 114 (19): 9319-9345

  View details for DOI 10.1021/cr500170p

  View details for Web of Science ID 000343017900003

  View details for PubMedID 25004056

• Enhanced Energy Transfer in Quasi-Quaternary Nanocrystal Superlattices ADVANCED MATERIALS Cargnello, M., Diroll, B. T., Gaulding, E. A., Murray, C. B. 2014; 26 (15): 2419-2423

  Abstract

  Quasi-quaternary nanocrystal superlattices are assembled by using exclusively core-shell particles as building blocks. The assemblies show an enhancement of energy-transfer from cadmium selenide-based core-shell quantum dots to gold-iron oxide core-shell nanocrystals compared to random mixtures of the same components.

  View details for DOI 10.1002/adma.201304136

  View details for Web of Science ID 000334181400019

  View details for PubMedID 24357329

• Control of Metal Nanocrystal Size Reveals Metal-Support Interface Role for Ceria Catalysts SCIENCE Cargnello, M., Doan-Nguyen, V. V., Gordon, T. R., Diaz, R. E., Stach, E. A., Gorte, R. J., Fornasiero, P., Murray, C. B. 2013; 341 (6147): 771-773

  Abstract

  Interactions between ceria (CeO2) and supported metals greatly enhance rates for a number of important reactions. However, direct relationships between structure and function in these catalysts have been difficult to extract because the samples studied either were heterogeneous or were model systems dissimilar to working catalysts. We report rate measurements on samples in which the length of the ceria-metal interface was tailored by the use of monodisperse nickel, palladium, and platinum nanocrystals. We found that carbon monoxide oxidation in ceria-based catalysts is greatly enhanced at the ceria-metal interface sites for a range of group VIII metal catalysts, clarifying the pivotal role played by the support.

  View details for DOI 10.1126/science.1240148

  View details for Web of Science ID 000323122200043

  View details for PubMedID 23868919

• Exceptional Activity for Methane Combustion over Modular Pd@CeO2 Subunits on Functionalized Al2O3 SCIENCE Cargnello, M., Delgado Jaen, J. J., Hernandez Garrido, J. C., Bakhmutsky, K., Montini, T., Calvino Gamez, J. J., Gorte, R. J., Fornasiero, P. 2012; 337 (6095): 713-717

  Abstract

  There is a critical need for improved methane-oxidation catalysts to both reduce emissions of methane, a greenhouse gas, and improve the performance of gas turbines. However, materials that are currently available either have low activity below 400°C or are unstable at higher temperatures. Here, we describe a supramolecular approach in which single units composed of a palladium (Pd) core and a ceria (CeO(2)) shell are preorganized in solution and then homogeneously deposited onto a modified hydrophobic alumina. Electron microscopy and other structural methods revealed that the Pd cores remained isolated even after heating the catalyst to 850°C. Enhanced metal-support interactions led to exceptionally high methane oxidation, with complete conversion below 400°C and outstanding thermal stability under demanding conditions.

  View details for DOI 10.1126/science.1222887

  View details for Web of Science ID 000307354500049

  View details for PubMedID 22879514

• Multiwalled Carbon Nanotubes Drive the Activity of Metal@oxide Core-Shell Catalysts in Modular Nanocomposites JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Cargnello, M., Grzelczak, M., Rodriguez-Gonzalez, B., Syrgiannis, Z., Bakhmutsky, K., La Parola, V., Liz-Marzan, L. M., Gorte, R. J., Prato, M., Fornasiero, P. 2012; 134 (28): 11760-11766

  Abstract

  Rational nanostructure manipulation has been used to prepare nanocomposites in which multiwalled carbon nanotubes (MWCNTs) were embedded inside mesoporous layers of oxides (TiO(2), ZrO(2), or CeO(2)), which in turn contained dispersed metal nanoparticles (Pd or Pt). We show that the MWCNTs induce the crystallization of the oxide layer at room temperature and that the mesoporous oxide shell allows the particles to be accessible for catalytic reactions. In contrast to samples prepared in the absence of MWCNTs, both the activity and the stability of core-shell catalysts is largely enhanced, resulting in nanocomposites with remarkable performance for the water-gas-shift reaction, photocatalytic reforming of methanol, and Suzuki coupling. The modular approach shown here demonstrates that high-performance catalytic materials can be obtained through the precise organization of nanoscale building blocks.

  View details for DOI 10.1021/ja304398b

  View details for Web of Science ID 000306457900068

  View details for PubMedID 22716042

• Nonaqueous Synthesis of TiO2 Nanocrystals Using TiF4 to Engineer Morphology, Oxygen Vacancy Concentration, and Photocatalytic Activity JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Gordon, T. R., Cargnello, M., Paik, T., Mangolini, F., Weber, R. T., Fornasiero, P., Murray, C. B. 2012; 134 (15): 6751-6761

  Abstract

  Control over faceting in nanocrystals (NCs) is pivotal for many applications, but most notably when investigating catalytic reactions which occur on the surfaces of nanostructures. Anatase titanium dioxide (TiO(2)) is one of the most studied photocatalysts, but the shape dependence of its activity has not yet been satisfactorily investigated and many questions still remain unanswered. We report the nonaqueous surfactant-assisted synthesis of highly uniform anatase TiO(2) NCs with tailorable morphology in the 10-100 nm size regime, prepared through a seeded growth technique. Introduction of titanium(IV) fluoride (TiF(4)) preferentially exposes the {001} facet of anatase through in situ release of hydrofluoric acid (HF), allowing for the formation of uniform anatase NCs based on the truncated tetragonal bipyramidal geometry. A method is described to engineer the percentage of {001} and {101} facets through the choice of cosurfactant and titanium precursor. X-ray diffraction studies are performed in conjunction with simulation to determine an average NC dimension which correlates with results obtained using electron microscopy. In addition to altering the particle shape, the introduction of TiF(4) into the synthesis results in TiO(2) NCs that are blue in color and display a broad visible/NIR absorbance which peaks in the infrared (λ(max) ≈ 3400 nm). The blue color results from oxygen vacancies formed in the presence of fluorine, as indicated by electron paramagnetic resonance (EPR) and X-ray photoelectron spectroscopy (XPS) studies. The surfactants on the surface of the NCs are removed through a simple ligand exchange procedure, allowing the shape dependence of photocatalytic hydrogen evolution to be studied using monodisperse TiO(2) NCs. Preliminary experiments on the photoreforming of methanol, employed as a model sacrificial agent, on platinized samples resulted in high volumes of evolved hydrogen (up to 2.1 mmol h(-1) g(-1)) under simulated solar illumination. Remarkably, the data suggest that, under our experimental conditions, the {101} facets of anatase are more active than the {001}.

  View details for DOI 10.1021/ja300823a

  View details for Web of Science ID 000302887300038

  View details for PubMedID 22444667

• Synthesis of Dispersible Pd@CeO2 Core-Shell Nanostructures by Self-Assembly JOURNAL OF THE AMERICAN CHEMICAL SOCIETY Cargnello, M., Wieder, N. L., Montini, T., Gorte, R. J., Fornasiero, P. 2010; 132 (4): 1402-1409

  Abstract

  A methodology is described for the preparation of Pd@CeO(2) core-shell nanostructures that are easily dispersible in common organic solvents. The method involves the synthesis of Pd nanoparticles protected by a monolayer of 11-mercaptoundecanoic acid (MUA). The carboxylic groups on the nanoparticle surfaces are used to direct the self-assembly of a cerium(IV) alkoxide around the metal particles, followed by the controlled hydrolysis to form CeO(2). The characterization of the nanostructures by means of different techniques, in particular by electron microscopy, allowed us to demonstrate the nature of core-shell systems, with CeO(2) nanocrystals forming a shell around the MUA-protected Pd core. Finally, an example of the use of these nanostructures as flexible precursors for the preparation of heterogeneous catalysts is reported by investigating the reactivity of Pd@CeO(2)/Al(2)O(3) nanocomposites toward CO oxidation, water-gas shift (WGS), and methanol steam reforming reactions. Together with CO adsorption data, these observations suggest the accessibility of the Pd phase in the nanocomposites.

  View details for DOI 10.1021/ja909131k

  View details for Web of Science ID 000275084800058

  View details for PubMedID 20043676