Atom trapping allows to prepare catalysts with atomically dispersed Ru ions anchored to the ceria support. The resulting catalysts free of expensive noble metals such as Pt, Pd, Rh (whose prices are ~8-60 times higher than Ru on the per-molar basis) with Ru loadings of only 0.25-0.5 wt% show excellent activity in industrially important catalytic NO oxidation reaction, a critical step that requires use of relatively large loadings of expensive noble metals in diesel aftertreatment systems. Ru1/CeO2 catalysts are stable during continuous cycling, ramping and cooling as well as presence of moisture. Furthermore, Ru1/CeO2 shows excellent NOx storage properties during cold start, with improved NO adsorption compared with the best described Pd/Zeolite NO adsorbers with ~2-3 times higher Pd loadings. We clarify the location of Ru(II) ions on the ceria surface and identify mechanism of NO oxidation (as well as reactive storage) using DFT calculations and in-situ DRIFTS/Mass-spectroscopy measurements. Furthermore, we show the possible applications of Ru1/CeO2 in gasoline engines for NO reduction by CO: only 0.1 wt% of atomically dispersed Ru is sufficient to achieve high activity at low temperatures. With the aid of excitation-modulation in-situ infra-red measurements, we uncover the elementary steps of NO reduction by CO on an atomically dispersed ceria-supported catalyst. Our study highlights the potential applicability of single-atom catalysts to industrially relevant NO and CO abatement.
Abstract The application of single‐atom catalysts (SACs) to high‐temperature hydrogenation requires materials that thermodynamically favor metal atom isolation over cluster formation. We demonstrate that Pd can be predominantly dispersed as isolated atoms onto TiO 2 during the reverse water–gas shift (rWGS) reaction at 400 °C. Achieving atomic dispersion requires an artificial increase of the absolute TiO 2 surface area by an order of magnitude and can be accomplished by physically mixing a precatalyst (Pd/TiO 2 ) with neat TiO 2 prior to the rWGS reaction. The in situ dispersion of Pd was reflected through a continuous increase of rWGS activity over 92 h and supported by kinetic analysis, infrared and X‐ray absorption spectroscopies and scanning transmission electron microscopy. The thermodynamic stability of Pd under high‐temperature rWGS conditions is associated with Pd‐Ti coordination, which manifests upon O‐vacancy formation, and the artificial increase in TiO 2 surface area.
Journal Article Controlling the Reaction Process in Operando STEM by Pixel Sub-Sampling Get access B Layla Mehdi, B Layla Mehdi Physical and Computational Science Directorate, PNNL, Richland, WA 99352, USA Search for other works by this author on: Oxford Academic Google Scholar Andrew Stevens, Andrew Stevens National Security Directorate, PNNL, Richland, WA 99352, USA Search for other works by this author on: Oxford Academic Google Scholar Libor Kovarik, Libor Kovarik Environmental Molecular Sciences Laboratory, PNNL, Richland, WA 99352, USA Search for other works by this author on: Oxford Academic Google Scholar Andrey Liyu, Andrey Liyu Environmental Molecular Sciences Laboratory, PNNL, Richland, WA 99352, USA Search for other works by this author on: Oxford Academic Google Scholar Bryan Stanfill, Bryan Stanfill National Security Directorate, PNNL, Richland, WA 99352, USA Search for other works by this author on: Oxford Academic Google Scholar Sarah Reehl, Sarah Reehl National Security Directorate, PNNL, Richland, WA 99352, USA Search for other works by this author on: Oxford Academic Google Scholar Lisa Bramer, Lisa Bramer National Security Directorate, PNNL, Richland, WA 99352, USA Search for other works by this author on: Oxford Academic Google Scholar Nigel D Browning Nigel D Browning Physical and Computational Science Directorate, PNNL, Richland, WA 99352, USAMaterials Science and Engineering, University of Washington, Seattle, WA 98195, USA Search for other works by this author on: Oxford Academic Google Scholar Microscopy and Microanalysis, Volume 23, Issue S1, 1 July 2017, Pages 98–99, https://doi.org/10.1017/S1431927617001179 Published: 04 August 2017
We studied Pt-Co bimetallic nanoparticles during oxidation in O2 and reduction in H2 atmospheres using an aberration corrected environmental transmission electron microscope. During oxidation Co migrates to the nanoparticle surface forming a strained epitaxial CoO film. It subsequently forms islands via strain relaxation. The atomic restructuring is captured as a function of time. During reduction cobalt migrates back to the bulk, leaving a monolayer of platinum on the surface.
Journal Article Structural Complexity and Loss of Long-range Order in θ-Al2O3 as Revealed by HAADF and Differential Phase Contrast Imaging Get access L Kovarik, L Kovarik Institute for Integrated Catalysis, Pacific Northwest National Laboratory, Richland, Washington, USA Search for other works by this author on: Oxford Academic Google Scholar K Khivantsev, K Khivantsev Institute for Integrated Catalysis, Pacific Northwest National Laboratory, Richland, Washington, USA Search for other works by this author on: Oxford Academic Google Scholar M Bowden, M Bowden Institute for Integrated Catalysis, Pacific Northwest National Laboratory, Richland, Washington, USA Search for other works by this author on: Oxford Academic Google Scholar J Szanyi J Szanyi Institute for Integrated Catalysis, Pacific Northwest National Laboratory, Richland, Washington, USA Search for other works by this author on: Oxford Academic Google Scholar Microscopy and Microanalysis, Volume 29, Issue Supplement_1, 1 August 2023, Pages 1794–1795, https://doi.org/10.1093/micmic/ozad067.928 Published: 22 July 2023
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