Gaurav Kamat

All Publications

• Electrolyte type affects electrochemical bubble formation. Nature chemistry Kamat, G. A., Burke Stevens, M. 2023

  View details for DOI 10.1038/s41557-023-01351-6

  View details for PubMedID 37872420

  View details for PubMedCentralID 10322699

• Acid anion electrolyte effects on platinum for oxygen and hydrogen electrocatalysis COMMUNICATIONS CHEMISTRY Kamat, G., Zeledon, J., Gunasooriya, G., Dull, S. M., Perryman, J. T., Norskov, J. K., Stevens, M., Jaramillo, T. F. 2022; 5 (1)

  View details for DOI 10.1038/s42004-022-00635-1

  View details for Web of Science ID 000757832500001

• Self-Limiting Shell Formation in Cu@Ag Core-Shell Nanocrystals during Galvanic Replacement JOURNAL OF PHYSICAL CHEMISTRY LETTERS Kamat, G. A., Yan, C., Osowiecki, W. T., Moreno-Hernandez, I. A., Ledendecker, M., Alivisatos, A. 2020; 11 (13): 5318–23

  Abstract

  The understanding of synthetic pathways of bimetallic nanocrystals remains limited due to the complex energy landscapes and dynamics involved. In this work, we investigate the formation of self-limiting Cu@Ag core-shell nanoparticles starting from Cu nanocrystals followed by galvanic replacement with Ag ions. Bulk quantification with atomic emission spectroscopy and spatially resolved elemental mapping with electron microscopy reveal distinct nucleation regimes that produce nanoparticles with a tunable Ag shell thickness, but only up to a certain limiting thickness. We develop a quantitative transport model that explains this observed self-limiting structure as arising from the balance between entropy-driven interdiffusion and a positive mixing enthalpy. The proposed model depends only on the intrinsic physical properties of the system such as diffusivity and mixing energy and directly yields a high level of agreement with the elemental mapping profiles without requiring additional fit parameters.

  View details for DOI 10.1021/acs.jpclett.0c01551

  View details for Web of Science ID 000547468400057

  View details for PubMedID 32530633

• Advancing Insights into Electrochemical Pre-Treatments of Supported Nanoparticle Electrocatalysts by Combining a Design of Experiments Strategy with In Situ Characterization ADVANCED ENERGY MATERIALS Mule, A. S., Tran, K., Aleman, A. M., Cornejo-Carrillo, Y. E., Kamat, G. A., Stevens, M., Jaramillo, T. F. 2024

  View details for DOI 10.1002/aenm.202401939

  View details for Web of Science ID 001285493200001

• Tuning Two-Dimensional Phthalocyanine Dual Site Metal-Organic Framework Catalysts for the Oxygen Reduction Reaction. Journal of the American Chemical Society Wei, L., Hossain, M. D., Chen, G., Kamat, G. A., Kreider, M. E., Chen, J., Yan, K., Bao, Z., Bajdich, M., Stevens, M. B., Jaramillo, T. F. 2024

  Abstract

  Metal-organic frameworks (MOFs) offer an interesting opportunity for catalysis, particularly for metal-nitrogen-carbon (M-N-C) motifs by providing an organized porous structural pattern and well-defined active sites for the oxygen reduction reaction (ORR), a key need for hydrogen fuel cells and related sustainable energy technologies. In this work, we leverage electrochemical testing with computational models to study the electronic and structural properties in the MOF systems and their relationship to ORR activity and stability based on dual transitional metal centers. The MOFs consist of two M1 metals with amine nodes coordinated to a single M2 metal with a phthalocyanine linker, where M1/M2 = Co, Ni, or Cu. Co-based metal centers, in particular Ni-Co, demonstrate the highest overall activity of all nine tested MOFs. Computationally, we identify the dominance of Co sites, relative higher importance of the M2 site, and the role of layer M1 interactions on the ORR activity. Selectivity measurements indicate that M1 sites of MOFs, particularly Co, exhibit the lowest (<4%), and Ni demonstrates the highest (>46%) two-electron selectivity, in good agreement with computational studies. Direct in situ stability characterization, measuring dissolved metal ions, and calculations, using an alkaline stability metric, confirm that Co is the most stable metal in the MOF, while Cu exhibits notable instability at the M1. Overall, this study reveals how atomistic coupling of electronic and structural properties affects the ORR performance of dual site MOF catalysts and opens new avenues for the tunable design and future development of these systems for practical electrochemical applications.

  View details for DOI 10.1021/jacs.4c02229

  View details for PubMedID 38709577

• Interpretable Machine Learning Models for Practical Antimonate Electrocatalyst Performance. Chemphyschem : a European journal of chemical physics and physical chemistry Deo, S., Kreider, M., Kamat, G., Hubert, M., Zamora Zeledón, J., Wei, L., Matthews, J., Keyes, N., Singh, I., Jaramillo, T., Abild-Pedersen, F., Burke Stevens, M., Winther, K., Voss, J. 2024: e202400010

  Abstract

  Computationally predicting the performance of catalysts under reaction conditions is a challenging task due to the complexity of catalytic surfaces and their evolution in situ, different reaction paths, and the presence of solid-liquid interfaces in the case of electrochemistry. We demonstrate here how relatively simple machine learning models can be found that enable prediction of experimentally observed onset potentials. Inputs to our model are comprised of data from the oxygen reduction reaction on non-precious transition-metal antimony oxide nanoparticulate catalysts with a combination of experimental conditions and computationally affordable bulk atomic and electronic structural descriptors from density functional theory simulations. From human-interpretable genetic programming models, we identify key experimental descriptors and key supplemental bulk electronic and atomic structural descriptors that govern trends in onset potentials for these oxides and deduce how these descriptors should be tuned to increase onset potentials. We finally validate these machine learning predictions by experimentally confirming that scandium as a dopant in nickel antimony oxide leads to a desired onset potential increase. Macroscopic experimental factors are found to be crucially important descriptors to be considered for models of catalytic performance, highlighting the important role machine learning can play here even in the presence of small datasets.

  View details for DOI 10.1002/cphc.202400010

  View details for PubMedID 38547332

• Tracking the Dynamics of a Ag-MnO x Oxygen Reduction Catalyst Using In Situ and Operando X-ray Absorption Near-Edge Spectroscopy ACS ENERGY LETTERS Schroder, J., Zamora Zeledon, J. A., Kamat, G. A., Kreider, M. E., Wei, L., Mule, A. S., Torres, A., Yap, K., Sokaras, D., Gallo, A., Stevens, M., Jaramillo, T. F. 2023

  View details for DOI 10.1021/acsenergylett.3c00823

  View details for Web of Science ID 001015819200001

• Hydrogen production with seawater-resilient bipolar membrane electrolyzers JOULE Marin, D. H., Perryman, J. T., Hubert, M. A., Lindquist, G. A., Chen, L., Aleman, A. M., Kamat, G. A., Niemann, V. A., Stevens, M., Regmi, Y. N., Boettcher, S. W., Nielander, A. C., Jaramillo, T. F. 2023; 7 (4): 765-781

  View details for DOI 10.1016/j.joule.2023.03.005

  View details for Web of Science ID 000988108000001

• Understanding the Stability of Manganese Chromium Antimonate Electrocatalysts through Multimodal In Situ and Operando Measurements. Journal of the American Chemical Society Kreider, M. E., Kamat, G. A., Zamora Zeledón, J. A., Wei, L., Sokaras, D., Gallo, A., Stevens, M. B., Jaramillo, T. F. 2022

  Abstract

  Improving electrocatalyst stability is critical for the development of electrocatalytic devices. Herein, we utilize an on-line electrochemical flow cell coupled with an inductively coupled plasma-mass spectrometer (ICP-MS) to characterize the impact of composition and reactant gas on the multielement dissolution of Mn(-Cr)-Sb-O electrocatalysts. Compared to Mn2O3 and Cr2O3 oxides, the antimonate framework stabilizes Mn at OER potentials and Cr at both ORR and OER potentials. Furthermore, dissolution of Mn and Cr from Mn(-Cr) -Sb-O is driven by the ORR reaction rate, with minimal dissolution under N2. We observe preferential dissolution of Cr totaling 13% over 10 min at 0.3, 0.6, and 0.9 V vs RHE, with only 1.5% loss of Mn, indicating an enrichment of Mn at the surface of the particles. Despite this asymmetric dissolution, operando X-ray absorption spectroscopy (XAS) showed no measurable changes in the Mn K-edge at comparable potentials. This could suggest that modification to the Mn oxidation state and/or phase in the surface layer is too small or that the layer is too thin to be measured with the bulk XAS measurement. Lastly, on-line ICP-MS was used to assess the effects of applied potential, scan rate, and current on Mn-Cr-Sb-O during cyclic voltammetry and accelerated stress tests. With this deeper understanding of the interplay between oxygen reduction and dissolution, testing procedures were identified to maximize both activity and stability. This work highlights the use of multimodal in situ characterization techniques in tandem to build a more complete model of stability and develop protocols for optimizing catalyst performance.

  View details for DOI 10.1021/jacs.2c08600

  View details for PubMedID 36453840

• 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

• Origins of wear-induced tungsten corrosion defects in semiconductor manufacturing during tungsten chemical mechanical polishing APPLIED SURFACE SCIENCE Choi, S., Kreider, M. E., Nielander, A. C., Stevens, M., Kamat, G., Koo, J., Bae, K., Kim, H., Yoon, I., Yoon, B., Hwang, K., Lee, D., Jaramillo, T. F. 2022; 598

  View details for DOI 10.1016/j.apsusc.2022.153767

  View details for Web of Science ID 000818529100002

• Facet-selective etching trajectories of individual semiconductor nanocrystals SCIENCE ADVANCES Yan, C., Byrne, D., Ondry, J. C., Kahnt, A., Moreno-Hernandez, I. A., Kamat, G. A., Liu, Z., Laube, C., Crook, M. F., Zhang, Y., Ercius, P., Alivisatos, A. 2022; 8 (32): eabq1700

  Abstract

  The size and shape of semiconductor nanocrystals govern their optical and electronic properties. Liquid cell transmission electron microscopy (LCTEM) is an emerging tool that can directly visualize nanoscale chemical transformations and therefore inform the precise synthesis of nanostructures with desired functions. However, it remains difficult to controllably investigate the reactions of semiconductor nanocrystals with LCTEM, because of the highly reactive environment formed by radiolysis of liquid. Here, we harness the radiolysis processes and report the single-particle etching trajectories of prototypical semiconductor nanomaterials with well-defined crystalline facets. Lead selenide nanocubes represent an isotropic structure that retains the cubic shape during etching via a layer-by-layer mechanism. The anisotropic arrow-shaped cadmium selenide nanorods have polar facets terminated by either cadmium or selenium atoms, and the transformation trajectory is driven by etching the selenium-terminated facets. LCTEM trajectories reveal how nanoscale shape transformations of semiconductors are governed by the reactivity of specific facets in liquid environments.

  View details for DOI 10.1126/sciadv.abq1700

  View details for Web of Science ID 000841491100034

  View details for PubMedID 35947667

• Engineering gold-platinum core-shell nanoparticles by self-limitation in solution COMMUNICATIONS CHEMISTRY Ledendecker, M., Paciok, P., Osowiecki, W. T., Pander, M., Heggen, M., Goehl, D., Kamat, G. A., Erbe, A., Mayrhofer, K. J., Alivisatos, A. 2022; 5 (1): 71

  Abstract

  Core-shell particles with thin noble metal shells represent an attractive material class with potential for various applications ranging from catalysis to biomedical and pharmaceutical applications to optical crystals. The synthesis of well-defined core-shell architectures remains, however, highly challenging. Here, we demonstrate that atomically-thin and homogeneous platinum shells can be grown via a colloidal synthesis method on a variety of gold nanostructures ranging from spherical nanoparticles to nanorods and nanocubes. The synthesis is based on the exchange of low binding citrate ligands on gold, the reduction of platinum and the subsequent kinetically hindered growth by carbon monoxide as strong binding ligand. The prerequisites for homogeneous growth are low core-binding ligands with moderate fast ligand exchange in solution, a mild reducing agent to mitigate homonucleation and a strong affinity of a second ligand system that can bind to the shell's surface. The simplicity of the described synthetic route can potentially be adapted to various other material libraries to obtain atomically smooth core-shell systems.

  View details for DOI 10.1038/s42004-022-00680-w

  View details for Web of Science ID 000806740600001

  View details for PubMedID 36697905

  View details for PubMedCentralID PMC9814372

• Methods-A Practical Approach to the Reversible Hydrogen Electrode Scale JOURNAL OF THE ELECTROCHEMICAL SOCIETY Zeledon, J., Jackson, A., Stevens, M., Kamat, G. A., Jaramillo, T. F. 2022; 169 (6)

  View details for DOI 10.1149/1945-7111/ac71d1

  View details for Web of Science ID 000806520100001

• Engineering metal-metal oxide surfaces for high-performance oxygen reduction on Ag-Mn electrocatalysts ENERGY & ENVIRONMENTAL SCIENCE Zeledon, J., Gunasooriya, G., Kamat, G. A., Kreider, M. E., Ben-Naim, M., Hubert, M. A., Acosta, J., Norskov, J. K., Stevens, M., Jaramillo, T. F. 2022

  View details for DOI 10.1039/d2ee00047d

  View details for Web of Science ID 000766715400001

• Rational solvent molecule tuning for high-performance lithium metal battery electrolytes NATURE ENERGY Yu, Z., Rudnicki, P. E., Zhang, Z., Huang, Z., Celik, H., Oyakhire, S. T., Chen, Y., Kong, X., Kim, S., Xiao, X., Wang, H., Zheng, Y., Kamat, G. A., Kim, M., Bent, S. F., Qin, J., Cui, Y., Bao, Z. 2022

  View details for DOI 10.1038/s41560-021-00962-y

  View details for Web of Science ID 000742253900001

• Probing the Effects of Acid Electrolyte Anions on Electrocatalyst Activity and Selectivity for the Oxygen Reduction Reaction CHEMELECTROCHEM Zamora Zeledon, J. A., Kamat, G., Gunasooriya, G., Norskov, J. K., Stevens, M., Jaramillo, T. F. 2021; 8 (13): 2467-2478

  View details for DOI 10.1002/celc.202100500

  View details for Web of Science ID 000674273100011

• Precise Colloidal Plasmonic Photocatalysts Constructed by Multistep Photodepositions NANO LETTERS Ha, H., Yan, C., Katsoukis, G., Kamat, G. A., Moreno-Hernandez, I. A., Frei, H., Alivisatos, A. 2020; 20 (12): 8661–67

  Abstract

  Natural photosynthesis relies on a sophisticated charge transfer pathway among multiple components with precise spatial, energetic, and temporal organizations in the aqueous environment. It continues to inspire and challenge the design and fabrication of artificial multicomponent colloidal nanostructures for solar-to-fuel conversion. Herein, we introduce a plasmonic photocatalyst synthesized with colloidal methods with five integrated components including cocatalysts installed in orthogonal locations. The precise deposition of individual inorganic components on an Au/TiO2 nanodumbell nanostructure is enabled by photoreduction and photo-oxidation, which selectively occurs at the TiO2 tip sites and Au lateral sites, respectively. Under visible-light irradiation, the photocatalyst exhibited activity of oxygen evolution from water without scavengers. We demonstrate that each component is essential for improving the photocatalytic performance. In addition, mechanistic studies suggest that the photocatalytic reaction requires combining the hot charge carriers derived from exciting both the d-sp interband transition and the localized surface plasmon resonance of Au.

  View details for DOI 10.1021/acs.nanolett.0c03431

  View details for Web of Science ID 000599507100036

  View details for PubMedID 33226246

• Factors and Dynamics of Cu Nanocrystal Reconstruction under CO2 Reduction ACS APPLIED ENERGY MATERIALS Osowiecki, W. T., Nussbaum, J. J., Kamat, G. A., Katsoukis, G., Ledendecker, M., Frei, H., Bell, A. T., Alivisatos, A. 2019; 2 (11): 7744–49

  View details for DOI 10.1021/acsaem.9b01714

  View details for Web of Science ID 000500038900006

• Low-dimensional perovskite nanoplatelet synthesis using in situ photophysical monitoring to establish controlled growth NANOSCALE Do, M., Kim, I., Kolaczkowski, M. A., Kang, J., Kamat, G. A., Yuan, Z., Barchi, N. S., Wang, L., Liu, Y., Jurow, M. J., Sutter-Fella, C. M. 2019; 11 (37): 17262–69

  Abstract

  Perovskite nanoparticles have attracted the attention of research groups around the world for their impressive photophysical properties, facile synthesis and versatile surface chemistry. Here, we report a synthetic route that takes advantage of a suite of soluble precursors to generate CsPbBr3 perovskite nanoplatelets with fine control over size, thickness and optical properties. We demonstrate near unit cell precision, creating well characterized materials with sharp, narrow emission lines at 430, 460 and 490 nm corresponding to nanoplatelets that are 2, 4, and 6 unit cells thick, respectively. Nanoplatelets were characterized with optical spectroscopy, atomic force microscopy, scanning electron microscopy and transmission electron microscopy to explicitly correlate growth conditions, thickness and resulting photophysical properties. Detailed in situ photoluminescence spectroscopic studies were carried out to understand and optimize particle growth by correlating light emission with nanoplatelet growth across a range of synthetic conditions. It was found that nanoplatelet thickness and emission wavelength increase as the ratio of oleic acid to oleyl amine or the reaction temperature is increased. Using this information, we control the lateral size, width and corresponding emission wavelength of the desired nanoplatelets by modulating the temperature and ratios of the ligand.

  View details for DOI 10.1039/c9nr04010b

  View details for Web of Science ID 000487944000040

  View details for PubMedID 31246216