Suppressing the competing hydrogen evolution reaction in CO₂ electroreduction: A review

The conversion of CO₂ to valuable chemical products via direct electrochemical reduction (CO₂RR) has emerged as a potential means to simultaneously reduce the impact of global warming and the dependency on fossil fuels. During the past several years, tremendous efforts have been made to develop an efficient and effective CO₂RR system. However, most currently developed CO₂RR systems still suffer from low faradaic efficiency due to the competing hydrogen evolution reaction (HER). Therefore, this review addresses the current advances and strategies to suppress the competing HER in CO₂RR. Herein, the general reaction mechanism of CO₂RR, HER, and the competing HER in CO₂RR are first described. Subsequently, various strategies in suppressing HER in CO₂RR, such as the type of electrocatalyst, the utilization of polymeric binder, the type of electrolyte, the utilization of gas diffusion electrode (GDE) cell, and other approaches, are also highlighted. This review concludes with a summary of the future outlook and challenges in implementing such technologies to develop more efficient CO₂ utilization and conversion.