Enhanced Activity and Selectivity for Electrochemical CO2 Reduction through Water Activation by Oxophilic Metal Deposited on Ag

Abstract

Converting CO2 to useful chemicals using electrocatalytic processes is a promising technology for reducing the amount of CO2 in the atmosphere. In the previous literature on metal-based catalysts, most attempts have focused on the optimization of CO2-reduction reactions using conventional approaches, including nanostructuring and morphology or composite control, which have inefficient and sluggish reaction kinetics-associated protonation steps. In this study, we present an innovative approach for the electrochemical CO2 reduction through bifunctional effect from oxophilic metal-incorporated Ag, facilitating the CO2 protonation step. The theoretical and experimental analyses demonstrate that the high oxophilicity of Co and Ni accelerates H2O activation and proton generation, providing a protonation pathway in addition to the direct pathway of CO2 by supplying additional protons. In addition, we confirmed that the oxophilic metal can introduce adsorption sites for stabilizing COOH* adsorption, where C and O in COOH* interact with Ag and Co (or Ni) sites, respectively. Thus, the Co- and Ni-incorporated Ag catalysts show much enhanced catalytic performance compared to pure Ag with a high selectivity for CO of 91.4 and 88.47% at −1.2 vs reversible hydrogen electrode (RHE). These results, highlighting the role of oxophilic metal sites exhibiting the bifunctional effect, will provide important clues for future catalyst design rules for efficient CO2 reduction.