Interfacial microenvironment effects on electrochemical CO2 reduction

Electrochemical reduction of carbon dioxide (ECR) powered by renewable energy has the potential to utilize the intermittent renewable electric energy, alleviate the problem of excessive CO2 emissions and yield high value-added chemicals. Despite the intrinsic activity of the well-designed catalysts, subtle changes in the electrode–electrolyte interface will have a significant impact on the overall reaction. The electrode and its microenvironment together determine the ECR performance. Revealing the relationship between the microenvironment of the catalyst-electrolyte interface and the ECR performance is critical for explaining the reaction mechanism and controlling the reaction process accurately. To maximize the catalytic performance includes the activity, selectivity and stability, the fundamental understanding of the interfacial microenvironment should be clarified as important as the intrinsic properties of the catalyst. Researches on the microenvironment in ECR have been gradually launched while the comprehensive discussion is scarcely. In this review, the interfacial microenvironment changes affected by multiple influence factors including the electrolyte effects (cation effect, anion effect, local pH, electrolyte type and concentration), morphological effects (tip effect, confinement effect), catalyst surface modification (surface hydrophobicity, chemical and electronic state) and electrolyzers improvement (gas diffusion electrode, membrane electrode reaction microenvironment control) are illustrated. Finally, some perspectives are offered on the basis of understanding the connection of catalytic activity and the interfacial microenvironment, these insights obtained can be applied for better control the CO2 reduction and rational design reactors.