Bimetallic and multi-component catalysts typically exhibit composition-dependent activity and selectivity, and when optimized often outperform single-component catalysts. Here we used ambient-pressure X-ray photoelectron spectroscopy (AP-XPS) and in situ and ex situ transmission electron microscopy (TEM) to elucidate the origin of composition dependence observed in the catalytic activities of monodisperse CoPd bimetallic nanocatalysts for CO oxidation. We found that the catalysis process induced a reconstruction of the catalysts, leaving CoOx on the nanoparticle surface. The synergy between Pd and CoOx coexisting on the surface promotes the catalytic activity of the bimetallic catalysts. This synergistic effect can be optimized by tuning the Co/Pd ratios in the nanoparticle synthesis, and it reaches a maximum at compositions near Co0.24Pd0.76, which achieves complete CO conversion at the lowest temperature. Our combined AP-XPS and TEM studies provide direct observation of the surface evolution of the bimetallic nanoparticles under catalytic conditions and show how this evolution correlates with catalytic properties.
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The data that support the plots within this paper and other findings of this study are available from the corresponding author upon reasonable request.
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This work was supported by the Office of Basic Energy Sciences of the US Department of Energy under contract no. DE-AC02-05CH11231 through the Chemical Sciences, Geosciences, and Biosciences Division. Funding from the same contract for the ALS and beamline 9.3.2 is also acknowledged. Partial work on CoPd nanoparticles synthesis and characterization were supported by US National Science Foundation (DMR-1809700) and Jeffress Trust Awards Program in Interdisciplinary Research from Thomas F. and Kate Miller Jeffress Memorial Trust. Partial work on electron microscopy carried out at the Center for Functional Nanomaterials, Brookhaven National Laboratory, was supported by the US Department of Energy, Office of Basic Energy Sciences, under contract no. DE-AC02-98CH10886.
The authors declare no competing interests.
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Wu, C.H., Liu, C., Su, D. et al. Bimetallic synergy in cobalt–palladium nanocatalysts for CO oxidation. Nat Catal 2, 78–85 (2019). https://doi.org/10.1038/s41929-018-0190-6
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