Advancements in electrochemical CO2 reduction reaction: A review on CO2 mass transport enhancement strategies

The imperative to address climate change and CO2 emissions has elicited substantial interest in the field of electrochemical CO2 reduction reaction (eCO2RR) as an avenue to both environmental sustainability and the production of value-added fuels. However, the selectivity and efficiency of eCO2RR remain below the industrial requirement for its implementation at high current density. One pivotal strategy to ameliorate this deficiency involves augmenting the mass transport of CO2 to electrode, thereby alleviating the competing hydrogen evolution reaction and consequently enhancing eCO2RR performance. Herein, we primarily discuss the CO2 mass transport enhancement strategies through electrode and electrolyzer designs, as well as electrolysis conditions. The electrode designs are first presented, including wettability regulation, porous substrates construction, catalyst layer and gas diffusion layer designs. Then, we highlight state-of-the-art electrolyzer designs, including the bipolar membrane structure, interdigitated flow field and in -situ exsolution of CO2 structure. The electrolyzer based gas-liquid Taylor flow is also introduced. Following this, we delve into the impact of various electrolysis conditions, encompassing the electrolyte, electrolysis potentials, CO2 pressure, CO2 flow rate and reaction temperature. Finally, we conclude this review by delineating persisting challenges and potential solutions aimed at advancing CO2 mass transport for the industrial implementation of eCO2RR technology.