The high catalytic performance of core–shell nanoparticles is usually attributed to their distinct geometric and electronic structures. Here we reveal a dynamic mechanism that overturns this conventional understanding by a direct environmental transmission electron microscopy visualization coupled with multiple state-of-the-art in situ techniques, which include synchrotron X-ray absorption spectroscopy, infrared spectroscopy and theoretical simulations. A Ni–Au catalytic system, which exhibits a highly selective CO production in CO2 hydrogenation, features an intact ultrathin Au shell over the Ni core before and after the reaction. However, the catalytic performance could not be attributed to the Au shell surface, but rather to the formation of a transient reconstructed alloy surface, promoted by CO adsorption during the reaction. The discovery of such a reversible transformation urges us to reconsider the reaction mechanism beyond the stationary model, and may have important implications not only for core–shell nanoparticles, but also for other well-defined nanocatalysts.
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All the data needed to support the plots and evaluate the conclusions within this article are present within it, the Supplementary Information or the Cambridge Crystallographic Data Centre (deposition no. CSD 1979031-1979068), or are available from the corresponding author upon reasonable request.
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This work received financial support from Talents Innovation Project of Dalian (2016RD04), CAS Youth Innovation Promotion Association (2019190) and the Natural Science Foundation of China (21773287, 11604357, 21872145, 21902019, 11574340 and 51874115); G.Z. and J.T.M. were supported in part by the National Science Foundation under Cooperative Agreement no. EEC-1647722. G.Z. also acknowledges the Fundamental Research Funds for Central Universities (DUT18RC(3)057). B.Z. thanks the financial support of the Key Research Program of Frontier Sciences, CAS, Grant no. ZDBS-LY-7012. Use of the Advanced Photon Source was supported by the US Department of Energy, Office of Basic Energy Sciences, under contract no. DE-AC02-06CH11357. MRCAT operations, beamline 10-BM, are supported by the Department of Energy and the MRCAT member institutions; the computational resources utilized in this research were provided by the National Supercomputing Center in Guangzhou (NSCC-GZ), Tianjin and Shanghai. In situ TEM work was also supported by NSFC 21802065 and was partially conducted at the picocenter of SUSTech CRF that receives funding from the Shenzhen government. We especially acknowledge H. Matsumoto and C. Zeng from Hitachi High-Technologies Co., Ltd, for the in situ STEM characterization; S. Liu from Dalian Jiaotong University for the focusing filtering and alignment on HRTEM images via scripting. This work is dedicated to the late D. Su for his valuable support and discussions.
The authors declare no competing interests.
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Supplementary methods, discussion, Figs. 1–20, Tables 1 and 2, and references.
In situ TEM video of the heating process at a pressure of ~9 mbar of 25% CO2 + 75% H2 from 500 to 600 °C at ×50 playback speed.
In situ TEM video of the cooling process at a pressure of ~9 mbar of 25% CO2 + 75% H2 from 600 to 400 °C at ×50 playback speed.
In situ SAED video of the heating process at a pressure of ~9 mbar of 25% CO2 + 75% H2 from 300 to 500 °C at ×10 playback speed.
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Zhang, X., Han, S., Zhu, B. et al. Reversible loss of core–shell structure for Ni–Au bimetallic nanoparticles during CO2 hydrogenation. Nat Catal 3, 411–417 (2020). https://doi.org/10.1038/s41929-020-0440-2
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