Confinement effect on the electrochemical CO2 reduction reaction

The CO2 electrochemical reduction reaction (CO2RR) is a promising alternative way to convert CO2 into high value-added fuels and chemicals with renewable electricity as an energy source to solve the current environmental problems. However, the low catalytic efficiency and poor stability of the CO2RR are challenges that need to be addressed. In this review, we summarize the advanced progress in the confinement effect on the CO2RR. In a confined environment, controlled diffusion behaviors of reactants, intermediates and products and charge transfer can effectively facilitate the CO2RR. Meanwhile, the local increase in pH due to the limited diffusion of the electrolyte and in situ-generated OH- can induce slow proton adsorption kinetics, resulting in inhibition of proton-involving reactions, especially the competitive reaction of hydrogen evolution. Besides, confinement structures can effectively stabilize active metal sites against corrosion, fragmentation, dissolution, agglomeration, and over-reduction due to the protection of limited space or/and confined intermediates. Therefore, attempts to illustrate the relationship between confinement architectures and their catalytic performance are necessary, and they are discussed in this review, and the current challenges and potential strategies for future CO2RR research are envisioned.