Interfacial Electrolyte Effects on Electrocatalytic CO2 Reduction

Electrocatalytic CO2 reduction (CO2RR), powered by renewable energy, has great potential in decreasing the concentration of CO2 in the atmosphere, as well as producing high value-added fuels or chemicals. The electrode and electrolyte together determine the catalytic performance of CO2RR. Despite the substantial progress has been made in the design and preparation of high-performance catalysts, the role of electrolyte at the electrode–electrolyte interface (EEI) which could largely affect the local catalytic environment has not been understood thoroughly. To maximize and balance the catalytic performance (i.e., activity, selectivity, and stability) of CO2RR from a standpoint of application, the fundamental understanding of interfacial electrolyte effects should be emphasized with equal importance to the intrinsic properties of the catalyst. In this Review, we will focus on the discussion of the role (effects) of electrolytes for CO2RR. We summarize the effects of electrolytes according to their compositions and local chemical environment, which include solvents, local pH, cations, anions, impurities, additives, and modifiers. In addition, in-depth investigations on the detection of intermediates during the catalytic reactions using in situ spectroscopy techniques are included. The mechanisms, current challenges, future developments, and perspectives are discussed.