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R. Sainju, D. Rathnayake, H. Tan, G. Bollas, A. M. Dongare, S. L. Suib, Y. Zhu*, ACS Nano, 2022
Highlights:
- Oxidation of metal nanocatalysts plays a significant role in catalyst activation, operation, deactivation, and regeneration
- In situ ETEM video combined with phase segmentation directly correlates particle-level oxidation kinetics with structural evolutions
- A unified oxidation theory is established to reconcile size-dependent Ni nanoparticle oxidation
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R. Sainju, S. Suib, C. Ding, Y. Zhu, Microscopy and Microanalysis, 2021, 27 (S1), 2216-2217.
Highlights:
- Unlike conventional sintering studies that rely mostly on measuring averaged nanoparticle size or the overall surface area, the nature of in situ ETEM offers direct real-time visualization of the nanoparticles’ evolution at the nanoscale in response to the different reactive gaseous environments
- Whether a nanoparticle was sintered or regenerated depends on the intricate interplays among the nanoparticle size, its surrounding nanoparticles, and the reaction conditions
- In-situ ETEM combined with deep learning-based computer vision holds the potential to register and scale up single-particle level analysis that is critical to the understanding of nanocatalyst regeneration
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M. Hu, L. Jin, Y. Zhu, L. Zhang, X. Lu, P. Kerns, X. Su, S. Cao, P. Gao, S. L. Suib, J. He*. Applied Catalysis B: Environmental, 264, 2020, 118553
Highlights:
- Under temperature reduction (UTR) was found in nanoalloy synthesis.
- Stable, ultrasmall and clean Pd-based nanoalloys were synthesized through UTR.
- Excellent ethanol electrooxidation and hydrogenation performances were achieved.
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M. Hu, W. Yang, H. Tan, L. Jin, L. Zhang, P. Kerns, Y. Dang, S. Dissanayake, S. Schaefer, B. Liu*, Y. Zhu*, S. L. Suib*, J. He*, Matter, 2, 2020, 1244-1259
Highlights:
- Template-free syntheses of mesoporous transition metal oxides are demonstrate
- Crystal interconversion results in highly crystalline frameworks
- Elimination of small molecules creates continuous porosity within oxides
- Unique surface-step defects boost the activity of porous oxides
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Design and synthesis of highly active MoVTeNb-oxides for ethane oxidative dehydrogenation.
D. Melzer, G. Mestl, K. Wanninger, Y. Zhu, N. D. Browning, M. Sanchez-Sanchez*, J. A. Lercher*, Nature Communication, 10, 2019, 1-9
Highlights:
- Highly active MoVTeNbOx (M1) catalysts have been directly and selectively synthesized with the aid of complexing agents that control the activities of ionic intermediates
- The formation of highly corrugated side walls for our M1 exposes a large concentration of active sites, leading to an unusually high intrinsic ethane ODH activity
Formation of Oxygen Radical Sites on MoVNbTeOx by Cooperative Electron Redistribution.
Y. Zhu*, P. V. Sushko, E. Jensen, L. Kovarik, D. Melzer, C. Ophus, M. Sanchez-Sanchez, J. A. Lercher* and N. D. Browning*, Journal of the American Chemical Society, 139, 2017, 12342-12345
Highlights:
- We report a novel pathway for increasing the surface density of catalytically active oxygen radical sites on a MoVTeNb oxide (M1 phase) catalyst during alkane oxidative dehydrogenation
- The reduction of a small fraction of Te4+ to Te0 in the Te-M1 catalyst generates redox-active O− radical sites under catalytic operating conditions, without compromising the structural integrity of the M1 catalyst.
- The in-situ ESTEM observations identify complex dynamic changes in the catalyst on an atomistic level, highlighting a new way to tailor structure and dynamics for highly active catalysts
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Y. Zhu*, N. D. Browning, ChemcatChem, 9, 2017, 3478-3485
Featured on the front cover of ChemcatChem and on MSA Update
Highlights:
- Gas environment effects on in-situ image quality and resolution are investigated experimentally and theoretically
- The absence of the extra inelastic noise owing to the annular collection mode of the ADF-STEM imaging allows the ESTEM imaging mode to maintain a good imaging SNR in gas
- Recent development in high-quality atomic ESTEM and other TEM advancements make it a promising in situ toolbox for investigating catalytic dynamics
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Location of Co and Ni promoter atoms in multi-layer MoS2 nanocrystals for hydrotreating catalysis.
Y. Zhu, Q. M. Ramasse, M. Brorson, P. G. Moses, L. P. Hansen, H. Topsøe, C. F. Kisielowski and S. Helveg*, Catalysis Today, 261, 2016, 75-81
Highlights:
- Aberration-corrected STEM and EELS spectrum imaging were used to determine the location of Co and Ni promoter atoms in industrial-style hydrotreating catalysts
- Both Co and Ni promoter atoms occupy sites at all low-indexed edge terminations of hexagonally shaped multi-layer MoS2 nanocatalyst
- Successive MoS2 multilayers alternatingly expose Mo- and S-edge terminations in any of the low-indexed directions, providing promoted edge sites with different steric accessibility for the organic compounds in mineral oil distillates
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D. Melzer, P. Xu, D. Hartmann, Y. Zhu, N. D. Browning, M. Sanchez-Sanchez and J. A. Lercher*, Angewandte Chemie International Edition, 55, 2016, 8873–8877
Highlights:
- Combination of quantitative analysis of rates with statistical analysis by HIM and HAADF-STEM allowed linking the macroscopic catalytic rates to the atomic level description of active surfaces for understanding selective oxidation catalysis on an atomistic level
- The lateral facets {120} and {210} expose crystalline positions related to the typical active centers described for propane oxidation; in contrast, the low activity of the facet {010} is attributed to stable M6O21 units connected by a single octahedron
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Visualizing the stoichiometry of industrial-style Co-Mo-S catalysts with single-atom sensitivity.
Y. Zhu, Q. M. Ramasse, M. Brorson, P. G. Moses, L. P. Hansen, C. F. Kisielowski and S. Helveg, Angewandte Chemie International Edition, 53, 2014, 10723-10727
Highlights:
- We answered a long-standing question on the Co-promotor atomic position in the so-called “Co-Mo-S” hydrotreating catalyst
- Single-atom-sensitive EELS spectrum imaging and HAADF-STEM pinpointed that the Co atoms occupy sites at the (100) S edge terminations of the MoS2 catalyst
- Specifically, each Co atom has four neighboring S atoms that are arranged in a reconstructed geometry, which reflects an equilibrium state