Opportunities and Challenges in CO2 Reduction by Gold- and Silver-Based Electrocatalysts: From Bulk Metals to Nanoparticles and Atomically Precise Nanoclusters

To tackle the excessive emission of greenhouse gas CO2, electrocatalytic reduction has been recognized as a promising way. Given the multielectron, multiproduct nature of the CO2 reduction process, an ideal catalyst should be capable of converting CO2 with high rates as well as high selectivity to either gas-phase (e.g., CO, CH4) or liquid-phase products (e.g., HCOOH, CH3OH, etc.). Gold- and silver-based materials have been extensively investigated as CO2 reduction catalysts for the formation of CO. This Perspective focuses on the advances of gold- and silver-based electrocatalysts for CO2 reduction in terms of catalyst design as well as some insights from theoretical investigations. In particular, a special emphasis is placed on the newly emerging, atomically precise metal nanoclusters for CO2 electroreduction. The strong quantum confinement effect and molecular purity as well as the crystallographically solved atomic structures of nanoclusters make this new class of catalysts quite promising in fundamental studies, and valuable mechanistic insights for CO2 electroreduction at the atomic scale can be obtained. We hope that this Perspective highlights the opportunities and challenges in the exploration of emerging nanomaterials.