Experimental and Theoretical Elucidation of Electrochemical CO₂ Reduction on an Electrodeposited Cu₃Sn Alloy

Abstract

The reaction selectivity of an electrode catalyst can be modulated by regulating its crystal structure, and the modified electrode may show different CO2 reduction selectivity from that of its constituent metal. In this study, we investigated the mechanisms of the electrochemical CO2 reduction on an electrodeposited Cu3Sn alloy by experimental and theoretical analyses. The electrodeposited Cu3Sn alloy electrode showed selectivity for CO production at all the applied potentials, and HCOOH production increased with an increase in the applied potential. In particular, hydrocarbon generation was well suppressed on Cu3Sn(002). To understand this selectivity change in electrochemical CO2 reduction, we conducted density functional theory calculations for the reaction on the Cu3Sn(002) surface. According to the theoretical analysis, the Cu sites in Cu3Sn(002) contributed more to the stabilization of H*, COOH*, and CO* as compared with the Sn sites. Furthermore, the results indicated that Cu3Sn(002) decreased the surface coverage of reaction intermediates such as H*, COOH*, and CO*. We believe that these effects promoted CO* desorption while suppressing H2 generation, CO* protonation, and C–C bond formation. The results also suggested that the surface Sn concentration significantly affected the reaction selectivity for HCOOH production from CO2.