Acidic conditions for efficient carbon dioxide electroreduction in flow and MEA cells

Electrochemical CO2 reduction reaction (CO2RR) under ambient conditions offers a promising way to reduce carbon emissions and achieve carbon neutrality. Although great progress has been made in both alkaline and neutral electrolytes, the carbon efficiency of CO2RR under these conditions is extremely low because of the formation and crossover of (bi)carbonates. In contrast, acidic conditions combined with cation exchange membranes can limit the formation and crossover of (bi)carbonates, leading to high carbon efficiency. Here we review the latest advances in electrochemical CO2RR in acidic media. The carbon efficiencies of CO2RR under alkaline, neutral, and acidic conditions are first introduced. Then we discuss the significant progress in CO2RR in acidic media and strategies for modulating performance in flow cells and membrane electrode assembly cells, followed by the catalyst development toward acidic CO2 electroreduction. Finally, we highlight research challenges and provide personal perspectives on CO2RR in acidic media.