Abstract
Ag-catalysed ethene epoxidation is the only viable route for making ethene oxide (EO) in industry, but the active site remains elusive due to the lack of tools to probe this reaction under high temperature and high-pressure conditions. Here, aided by advanced machine-learning grand canonical global structure exploration and in situ experiments, we identify a unique surface oxide phase, namely O5 phase, grown on Ag(100) under industrial catalytic conditions. This phase features square-pyramidal subsurface O and strongly adsorbed ethene, which can selectively convert ethene to EO. The other Ag surface facets, although also reconstructing to surface oxide phases, only contain surface O and produce CO2. The complex in situ surface phases with distinct selectivity contribute to an overall medium (50%) selectivity of Ag catalyst to EO. Our further catalysis experiments with in situ infra-red spectroscopy confirm the theory-predicted infra-red-active C=C vibration of adsorbed ethene on O5 phase and the microkinetics simulation results.
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Data availability
All data generated or analysed during this study are included in this published article (and its supplementary information files). Data are also available from the corresponding author upon request.
Code availability
The software code for LASP and the NN potentials used within the article are available from the corresponding author upon request or on the website: LASP software, http://www.lasphub.com; the LASP binary code for the Ag–C–H–O system, http://www.lasphub.com/supportings/lasp-free.tgz, and Ag–C–H–O G-NN potential, http://www.lasphub.com/supportings/AgCHO.pot.
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Acknowledgements
This work received financial support from the National Science Foundation of China (12188101, 22033003, 91945301, 91745201, 92145302, 22122301 and 92061112), Fundamental Research Funds for the Central Universities (20720220011) and the Tencent Foundation for XPLORER PRIZE.
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Z.-P.L. conceived the project and guided the research. D.C. designed and performed the theoretical simulations. L.C. designed and performed the experiments. Q.-C.Z. helped on the experiments. Z.-X.Y. helped on the code development and data analysis for the simulation of infra-red spectrum, C.S. helped on the code development. D.C. and L.C. drafted the manuscript. All authors discussed the manuscript and agreed with the content.
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Supplementary Figs. 1–32, Tables 1–11 and Notes 1–5.
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XYZ coordinates for the surface phases and transition states. List data include the VASP POSCAR format of all four major phases (listed are supercell models for reaction pathway calculations) of Ag catalyst under reaction conditions, and the key transition states in their corresponding reaction pathways. An INCAR sample for DFT calculation is also appended to this file.
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Chen, D., Chen, L., Zhao, QC. et al. Square-pyramidal subsurface oxygen [Ag4OAg] drives selective ethene epoxidation on silver. Nat Catal (2024). https://doi.org/10.1038/s41929-024-01135-2
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DOI: https://doi.org/10.1038/s41929-024-01135-2