Facet-Dependent Selectivity of Cuprous Oxide/Silver Tandem Catalysts for Promoting C2H4 Production from Electrochemical CO2 Reduction

Abstract

The over-exploitation of fossil fuels and the consequent increase of atmospheric CO2 concentration have aroused people's attention to energy and environmental issues.(1) In terms of reducing CO2 content, the electrocatalytic CO2 reduction reaction (CO2RR) can effectively solidify CO2 and convert it into high value-added chemicals. There are many CO2RR reduction products, including CO, HCOOH, C2H5OH, CH4,C2H4, etc.(2) However, in the CO2RR process, the hydrogen evolution reaction (HER) in the water phase has a lower reduction potential, making the CO2RR products less selective, which has become the most important problem restricting its practical application. Therefore, improving the selectivity and activity of CO2RR products has important research significance and practical application value.In this work, a series of Cu2O/Ag nanocrystals (NCs) with different crystal faces were prepared by hydrothermal method. Specifically, cubic Cu2O (c-Cu2O) enclosed with {100} facets, rhombic dodecahedral Cu2O (d-Cu2O) enclosed with {110} facets, and octahedral Cu2O (o-Cu2O) enclosed with {111} facets, are mixed with Ag nanospheres to form c-Cu2O/Ag, d-Cu2O/Ag, and o-Cu2O/Ag bimetallic tandem catalysts. The catalysts can improve the high activity and selectivity of CO2RR to produce C2H4 product by adjusting different crystal faces. We can find from Figure 1 that o-Cu2O/Ag tandem catalyst exhibits an impressive Faradaic efficiency (66.8%) and partial current density (17.8 mA cm-2) for C2H4 product at -1.2 VRHE. This result provides a new strategy for improving the selectivity of CO2RR to produce C2+ products by adjusting the crystal facet engineering. Figure 1. (a) SEM images of o-Cu2O/Ag, (b) LSV curves of three Cu2O/Ag catalysts in Ar and CO2-saturated 0.5 M KHCO3 solutions, (c) Partial current density of C2H4 formation on the three Cu2O/Ag catalysts at -1.2 V, (d) Faradaic efficiencies of C2H4 on the three Cu2O/Ag NCs. Reference [1] P. De Luna, C. Hahn, D. Higgins, S. A. Jaffer, T. F. Jaramillo and E. H. Sargent, Science, 364 (2019).[2]Y. Zheng, A. Vasileff, X. Zhou, Y. Jiao, M. Jaroniec and S. Z. Qiao, J Am Chem Soc, 141, 7646 (2019). Figure 1