Mass transfer effect to electrochemical reduction of CO₂: Electrode, electrocatalyst and electrolyte

Electrochemical carbon dioxide reduction reaction (eCO₂RR) to value-added chemicals is considered as a promising strategy for CO₂ conversion with economic and environmental benefits. Recently, investigations in eCO₂RR to produce chemicals as energy or chemical industrial feedstock have received much attention. The eCO₂RR generally occurs at the interface between electrode/electrocatalyst and electrolyte including charge transfer, phase transformation and mass transport. One of key problems in the electrochemical reaction is mass transfer limitation owing to the gaseous property of CO₂ with low concentration on the surface of electrode/electrocatalyst. Several strategies were employed to improve mass transfer in the past years, including electrochemical reactors, electrodes, electrocatalysts and electrolytes, etc. which could low reaction barriers so adequately that reaction rates can be realized that are sufficient for eCO₂RR. This article comprehensively reviewed development related to mass transfer study of CO₂, including the mechanism of mass transfer of CO₂, and main factors (electrodes, electrocatalysts and electrolytes) on two-phase or multi-phase interface during eCO₂RR. The article is not aim at providing a comprehensive review of technical achievements towards eCO₂RR technology, but rather to highlight electrode, catalyst, electrolyte, and other factors, which can understand the above components or factors' effects towards mass transfer investigations, to decouple mass transfer limitations and improve the performance of electrochemical CO₂ conversion. Furthermore, the challenges and perspectives for mass transfer to eCO₂RR are proposed.