Tin Oxide Catalysts for Formate-Selective Electrochemical Reduction of CO₂

Abstract

Electrochemical reduction of CO 2 (eCO2RR) to multicarbon products in aqueous solution is an important and challenging study to overcome the global climate change issue. Many recent mechanistic studies reported electrochemical CO 2 reductions in different aspects such as intermediate species, reaction paths, reaction rate-determining steps(RDSs), and the influence of electrolyte. Unfortunately, the reaction selectivity of C2+ products is still limited because the identification of RDS, as the most critical mechanism guide, still lacks comprehensive and convincing evidence. Currently, two mechanisms have been generally proposed as the potential RDS through theoretical calculation(density function theory, DFT), including *CO-*CO coupling and the protonation of *CO to *CO(H). Here, we prepared Ag-decorated Cu(I) oxide to perform electrochemical CO 2 reduction to C2+ with high reaction selectivity. The prepared Cu 2 O-Ag catalyst shows up to 35.4 % and 30.1 % C 2 H 4 and ethanol selectivity, respectively in CO 2 -saturated 0.1 M KHCO 3 electrolyte. In the eCO2RR, Ag nanoparticles (Ag NPs) are known as a selective CO 2 to CO conversion catalyst showing over 90 % reaction selectivity (Faradaic efficiency, FE). Hence, the decorated Ag NPs reduce the energy barrier of CO 2 to CO conversion, thereby producing C2+ products(C 2 H 4 , ethanol) by facilitating *CO-*CO coupling on the Cu catalyst surface. To clarify the reaction mechanism on the Cu surface, in-situ Raman has been evaluated and revealed CO*, CH*, and OH* reaction intermediate signals at different applied potentials. This work clarifies the RDS of C2+ production in eCO2RR, and the different roles of Ag NPs in (100) and (111) Cu crystal facets. Figure 1