Junjie Chen

All Publications

• Structural Transformation and Degradation of Cu Oxide Nanocatalysts during Electrochemical CO2 Reduction. Journal of the American Chemical Society Lee, S. H., Avilés Acosta, J. E., Lee, D., Larson, D. M., Li, H., Chen, J., Lee, J., Erdem, E., Lee, D. U., Blair, S. J., Gallo, A., Zheng, H., Nielander, A. C., Tassone, C. J., Jaramillo, T. F., Drisdell, W. S. 2025

  Abstract

  The electrochemical CO2 reduction reaction (CO2RR) holds enormous potential as a carbon-neutral route to the sustainable production of fuels and platform chemicals. The durability for long-term operation is currently inadequate for commercialization, however, and the underlying deactivation process remains elusive. A fundamental understanding of the degradation mechanism of electrocatalysts, which can dictate the overall device performance, is needed. In this work, we report the structural dynamics and degradation pathway of Cu oxide nanoparticles (CuOx NPs) during the CO2RR by using in situ small-angle X-ray scattering (SAXS) and X-ray absorption spectroscopy (XAS). The in situ SAXS reveals a reduction in the size of NPs when subjected to a potential at which no reaction products are detected. At potentials where the CO2RR starts to occur, CuOx NPs are agglomerated through a particle migration and coalescence process in the early stage of the reaction, followed by Ostwald ripening (OR) as the dominant degradation mechanism for the remainder of the reaction. As the applied potential becomes more negative, the OR process becomes more dominant, and for the most negative applied potential, OR dominates for the entire reaction time. The morphological changes are linked to a gradual decrease in the formation rate for multicarbon products (C2H4 and ethanol). Other reaction parameters, including reaction intermediates and local high pH, induce changes in the agglomeration process and final morphology of the CuOx NPs electrode, supported by post-mortem ex situ microscopic analysis. The in situ XAS analysis suggests that the CuOx NPs reduced into the metallic state before the structural transformation was observed. The introduction of high surface area carbon supports with ionomer coating mitigates the degree of structural transformation and detachment of the CuOx NPs electrode. These findings show the dynamic nature of Cu nanocatalysts during the CO2RR and can serve as a rational guideline toward a stable catalyst system under electrochemical conditions.

  View details for DOI 10.1021/jacs.4c14720

  View details for PubMedID 39815387

• <i>Operando</i> Surface-Enhanced Infrared Spectroscopy Connects Interfacial Dynamics with Reaction Kinetics During Electrochemical CO₂ Reduction on Copper ACS CATALYSIS Matthews, J. E., Acosta, J., Lee, S., Oh, D., Lin, T. Y., Yap, K. K., Chen, J., Jang, J., Lee, D., Nielander, A. C., Jaramillo, T. F. 2024

  View details for DOI 10.1021/acscatal.4c05532

  View details for Web of Science ID 001380955800001

• 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

• Condition-dependent NO<i>_x</i> adsorption/desorption over Pd/BEA: A combined microreactor and in situ DRIFTS study AICHE JOURNAL Chen, J., Lee, J., Khatri, P., Toops, T. J., Kyriakidou, E. A. 2024

  View details for DOI 10.1002/aic.18400

  View details for Web of Science ID 001176490500001

• Designing ultrastable Pt/CeO2-Al2O3 nanosheet catalysts for three-way catalysts applications CHEMICAL ENGINEERING JOURNAL Chen, J., Liu, C., Pham, H. N., Toops, T. J., Datye, A. K., Kyriakidou, E. A. 2023; 477

  View details for DOI 10.1016/j.cej.2023.147086

  View details for Web of Science ID 001110452300001

• Mechanistic Insights into Aldehyde Production from Electrochemical CO2 Reduction on CuAg Alloy via Operando X-ray Measurements ACS CATALYSIS Qiao, Y., Kastlunger, G., Davis, R. C., Rodriguez, C., Vishart, A., Deng, W., Xu, Q., Li, S., Benedek, P., Chen, J., Schro''der, J., Perryman, J., Lee, D., Jaramillo, T. F., Chorkendorff, I., Seger, B. 2023: 9379-9391

  View details for DOI 10.1021/acscatal.3c01009

  View details for Web of Science ID 001020631700001

• Ni/CeO2 Nanocatalysts with Optimized CeO2 Support Morphologies for CH4 Oxidation ACS APPLIED NANO MATERIALS Chen, J., Pham, H. N., Mon, T., Toops, T. J., Datye, A. K., Li, Z., Kyriakidou, E. A. 2023

  View details for DOI 10.1021/acsanm.2c05496

  View details for Web of Science ID 000946519900001

• Enhanced low temperature performance of bimetallic Pd/Pt/SiO2(core) @Zr(shell) diesel oxidation catalysts APPLIED CATALYSIS B-ENVIRONMENTAL Liu, C., Porter, S., Chen, J., Pham, H., Peterson, E. J., Khatri, P., Toops, T. J., Datye, A., Kyriakidou, E. A. 2023; 327

  View details for DOI 10.1016/j.apcatb.2023.122436

  View details for Web of Science ID 001003599700001

• Producing ultrastable Ni-ZrO2 nanoshell catalysts for dry reforming of methane by flame synthesis and Ni exsolution CHEM CATALYSIS Liu, S., Dun, C., Shah, M., Chen, J., Rao, S., Wei, J., Kyriakidou, E. A., Urban, J. J., Swihart, M. T. 2022; 2 (9): 2262-2274

  View details for DOI 10.1016/j.checat.2022.05.013

  View details for Web of Science ID 000903679200018

• Hydrogen generation via ammonia decomposition on highly efficient and stable Ru-free catalysts: approaching complete conversion at 450 degrees C ENERGY & ENVIRONMENTAL SCIENCE Tabassum, H., Mukherjee, S., Chen, J., Holiharimanana, D., Karakalos, S., Yang, X., Hwang, S., Zhang, T., Lu, B., Chen, M., Tang, Z., Kyriakidou, E. A., Ge, Q., Wu, G. 2022; 15 (10): 4190-4200

  View details for DOI 10.1039/d1ee03730g

  View details for Web of Science ID 000847701800001

• Effect of cobalt incorporation on the stability of ionic Pd in the presence of carbon monoxide over Pd/BEA passive NOx adsorbers CHEMICAL ENGINEERING JOURNAL Lee, J., Chen, J., Giewont, K., Mon, T., Liu, C., Walker, E. A., Kyriakidou, E. A. 2022; 440

  View details for DOI 10.1016/j.cej.2022.135834

  View details for Web of Science ID 000795186900003

• A General Route to Flame Aerosol Synthesis and in situ Functionalization of Mesoporous Silica. Angewandte Chemie (International ed. in English) Liu, S., Dun, C., Chen, J., Rao, S., Shah, M., Wei, J., Chen, K., Xuan, Z., Kyriakidou, E. A., Urban, J. J., Swihart, M. T. 2022

  Abstract

  Mesoporous silica is a versatile material for energy, environmental, and medical applications. Here, for the first time, we report a flame aerosol synthesis method for a class of mesoporous silica with hollow structure and specific surface area exceeding 1000 m 2 /g. We show its superior performance in water purification, drug carrier, and thermal insulation. Moreover, we propose a general route to produce mesoporous nanoshell supported nanocatalysts by in situ decorating active nanoclusters, including noble metal (Pt/SiO 2 ), transition metal (Ni/SiO 2 ), metal oxide (CrO 3 /SiO 2 ), and alumina support (Co/Al 2 O 3 ). As a prototypical application, we perform dry reforming of methane using Ni/SiO 2 , achieving constant 97% CH 4 and CO 2 conversions for more than 200 hours, dramatically outperforming MCM-41 supported Ni catalyst. This work provides a scalable strategy to produce mesoporous nanoshells and proposes an in situ functionalization mechanism to flexible catalysts design for many reactions.

  View details for DOI 10.1002/anie.202206870

  View details for PubMedID 35773200

• Hydrothermally stable Pd/SiO2@Zr Core@Shell catalysts for diesel oxidation applications CHEMICAL ENGINEERING JOURNAL Liu, C., Chen, J., Toops, T. J., Choi, J., Thomas, C., Lance, M. J., Kyriakidou, E. A. 2021; 425

  View details for DOI 10.1016/j.cej.2021.130637

  View details for Web of Science ID 000707126000101

• Ag/ZSM-5 traps for C2H4 and C7H8 adsorption under cold-start conditions MICROPOROUS AND MESOPOROUS MATERIALS Lee, J., Giewont, K., Chen, J., Liu, C., Walker, E. A., Kyriakidou, E. L. 2021; 327

  View details for DOI 10.1016/j.micromeso.2021.111428

  View details for Web of Science ID 000703780400001

• Cobalt-Induced PdO Formation in Low-Loading Pd/BEA Catalysts for CH4 Oxidation ACS CATALYSIS Chen, J., Giewont, K., Walker, E. A., Lee, J., Niu, Y., Kyriakidou, E. A. 2021; 11 (21): 13066-13076

  View details for DOI 10.1021/acscatal.1c00400

  View details for Web of Science ID 000716773800023

• Mechanistic Understanding of Methane Combustion over Ni/CeO2: A Combined Experimental and Theoretical Approach ACS CATALYSIS Chen, J., Buchanan, T., Walker, E. A., Toops, T. J., Li, Z., Kunal, P., Kyriakidou, E. A. 2021; 11 (15): 9345-9354

  View details for DOI 10.1021/acscatal.1c01088

  View details for Web of Science ID 000684035000033

• Hollow nanosphere construction of covalent organic frameworks for catalysis: (Pd/C)@TpPa COFs in Suzuki coupling reaction JOURNAL OF COLLOID AND INTERFACE SCIENCE Li, Y., Pei, B., Chen, J., Bing, S., Hou, L., Sun, Q., Xu, G., Yao, Z., Zhang, L. 2021; 591: 273-280

  Abstract

  A novel catalyst with a yolk-shell structure was designed to overcome the leaching of noble metals in heterogeneous catalysis. Through a template method, palladium (Pd) nanoparticles were encapsulated by hollow spherical covalent organic frameworks (COFs) consisting of 2,4,6-trihydroxybenzene-1,3,5-tricarbaldehyde (Tp) and p-phenylenediamine (Pa). The final catalyst with a yolk-shell structure was denoted as (Pd/C)@TpPa COFs. The unique morphology and chemical structure of this novel composite (Pd/C)@TpPa COFs were confirmed by a transmission electron microscope (TEM), a laser particle analyzer, X-ray diffraction (XRD), and N2 adsorption and desorption. Subsequently, to demonstrate its catalytic performance brought by structural design, this novel catalyst was applied to catalyze the Suzuki reaction. Interestingly, this catalyst exhibited a brilliant size cutoff efficiency for aryl benzene amounting to 100% and achieved a high conversion with only 0.05 mol% Pd loading. Besides, this catalyst could be readily recovered via filtration and reused for at least five consecutive cycles without any significant loss in its activity.

  View details for DOI 10.1016/j.jcis.2021.01.105

  View details for Web of Science ID 000632770200013

  View details for PubMedID 33607401

• Single-Step Flame Aerosol Synthesis of Active and Stable Nanocatalysts for the Dry Reforming of Methane ACS APPLIED MATERIALS & INTERFACES Mohammadi, M., Shah, C., Dhandapani, S., Chen, J., Abraham, S., Sullivan, W., Buchner, R. D., Kyriakidou, E. A., Lin, H., Lund, C. F., Swihart, M. T. 2021; 13 (15): 17618-17628

  Abstract

  We introduce a flame-based aerosol process for producing supported non-noble metal nanocatalysts from inexpensive aqueous metal salt solutions, using catalysts for the dry reforming of methane (DRM) as a prototype. A flame-synthesized nickel-doped magnesia (MgO) nanocatalyst (NiMgO-F) was fully physicochemically characterized and tested in a flow reactor system, where it showed stable DRM activity from 500 to 800 °C. A kinetic study was conducted, and apparent activation energies were extracted for the temperature range of 500-650 °C. It was then compared with a Ni-decorated MgO nanopowder prepared by wet impregnation of (1) flame-synthesized MgO (NiMgO-FI) and (2) a commercial MgO nanopowder (NiMgO-CI) and with (3) a NiMgO catalyst prepared by co-precipitation (NiMgO-CP). NiMgO-F showed the highest catalytic activity per mass and per metallic surface area and was stable for continuous H2 production at 700 °C for 50 h. Incorporation of potential promoters and co-catalysts was also demonstrated, but none showed significant performance improvement. More broadly, nanomaterials produced by this approach could be used as binary or multicomponent catalysts for numerous catalytic processes.

  View details for DOI 10.1021/acsami.1c02180

  View details for Web of Science ID 000643578300044

  View details for PubMedID 33821611

• Methane Combustion Over Ni/Ce(x)Zr(1-x)O(2)Catalysts: Impact of Ceria/Zirconia Ratio CHEMCATCHEM Chen, J., Carlson, B. D., Toops, T. J., Li, Z., Lance, M. J., Karakalos, S. G., Choi, J., Kyriakidou, E. A. 2020; 12 (21): 5558-5568

  View details for DOI 10.1002/cctc.202000947

  View details for Web of Science ID 000568807700001

• Boron-hyperdoped silicon for the selective oxidative dehydrogenation of propane to propylene CHEMICAL COMMUNICATIONS Chen, J., Rohani, P., Karakalos, S. G., Lance, M. J., Toops, T. J., Swihart, M. T., Kyriakidou, E. A. 2020; 56 (68): 9882-9885

  Abstract

  Boron containing catalysts have great potential in the oxidative dehydrogenation of propane. Herein, a series of 15, 25 and 42 at% boron-hyperdoped silicon catalysts synthesized by laser pyrolysis was studied. Boron-hyperdoped silicon samples showed >6 times higher propylene productivity than commercial h-BN at 450 °C.

  View details for DOI 10.1039/d0cc02822c

  View details for Web of Science ID 000562378500028

  View details for PubMedID 32720653

• Hyperbranched poly(amidoamine)/TMC reverse osmosis membrane for oily saline water treatment ENVIRONMENTAL TECHNOLOGY Pei, B., Chen, J., Liu, P., He, T., Li, X., Zhang, L. 2019; 40 (21): 2779-2788

  Abstract

  Generally, conventional polyamide reverse osmosis (RO) membranes suffer from a low water flux and serious oil pollution in the treatment of oil saline wastewater. Here, a novel RO membrane was successfully fabricated with hyperbranched polyamidoamine (PAMAM) and trimesoyl chloride (TMC) by interfacial reaction on polysulfone ultrafiltration membrane surface. The relatively smooth and thin PAMAM and TMC crosslinking active layer on the substrate membrane endowed the composite membrane with an excellent separation performance and remarkable anti-fouling performance simultaneously. For the stable saline emulsion with an oil droplet size of 300 nm, the rejection of oil and NaCl reached to 99% and 89.3% respectively, and the water flux was about 18.42 L/(m2h). After 24-h continuous operation, the rejection of oil and salt maintained above 98% and 88%, and the flux only decreased about 5%, exhibiting a more excellent resistance to oil pollution than the commercial membrane, of which the flux sharply decreased by 30%. Hence, it is believed that such membrane has great potential for effective separation of oily saline wastewater.

  View details for DOI 10.1080/09593330.2018.1452982

  View details for Web of Science ID 000477902200005

  View details for PubMedID 29536785

• Enhanced effect of daytime restricted feeding on the circadian rhythm of streptozotocin-induced type 2 diabetic rats AMERICAN JOURNAL OF PHYSIOLOGY-ENDOCRINOLOGY AND METABOLISM Wu, T., ZhuGe, F., Sun, L., Ni, Y., Fu, O., Gao, G., Chen, J., Kato, H., Fu, Z. 2012; 302 (9): E1027-E1035

  Abstract

  There is increasing awareness of the link between impaired circadian clocks and multiple metabolic diseases. However, the impairment of the circadian clock by type 2 diabetes has not been fully elucidated. To understand whether and how the function of circadian clock is impaired under the diabetic condition, we examined not only the expression of circadian genes in the heart and pineal gland but also the behavioral rhythm of type 2 diabetic and control rats in both the nighttime restricted feeding (NRF) and daytime restricted feeding (DRF) conditions. In the NRF condition, the circadian expression of clock genes in the heart and pineal gland was conserved in the diabetic rats, being similar to that in the control rats. DRF shifted the circadian phases of peripheral clock genes more efficiently in the diabetic rats than those in the control rats. Moreover, the activity rhythm of rats in the diabetic group was completely shifted from the dark phase to the light phase after 5 days of DRF treatment, whereas the activity rhythm of rats in the control group was still under the control of the suprachiasmatic nucleus (SCN) after the same DRF treatment. Furthermore, the serum glucose rhythm of type 2 diabetic rats was also shifted and controlled by the external feeding schedule, ignoring the SCN rhythm. Therefore, DRF shows stronger effect on the reentrainment of circadian rhythm in the type 2 diabetic rats, suggesting that the circadian system in diabetes is unstable and more easily shifted by feeding stimuli.

  View details for DOI 10.1152/ajpendo.00651.2011

  View details for Web of Science ID 000303593600002

  View details for PubMedID 22318948