Enhancing C-C Coupling in CO2 Electroreduction by Engineering Pore Size of Porous Carbon-Supported Cu Catalysts

The electroreduction of CO2 (CO2RR) is a promising and environmentally sustainable approach to closing the carbon cycle. However, achieving high activity and selectivity for multicarbon (C2₊) products remains a significant challenge due to the complexity of reaction pathways. In this study, porous carbon-supported copper catalysts (CuHCS) with pore sizes of 120 nm (CuHCS120) and 500 nm (CuHCS500) were synthesized to tailor the microenvironment at the electrode–electrolyte interface and enhance product selectivity. CuHCS120 achieved a maximum faradaic efficiency (FE) for C2₊ products of 46%, double that of CuHCS500 (23%). In contrast, CuHCS500 showed a higher FE for CO (36%) compared to CuHCS120 (14%) at the same potential. In-depth ex situ and in situ investigations revealed that smaller pores promote the enrichment and adsorption of *CO intermediates, thereby enhancing C–C coupling and the formation of C2₊ products. These findings underscore the critical role of structural confinement in modulating the catalytic microenvironment and provide valuable insights for the rational design of advanced catalysts for CO2RR.