Challenges and strategies for CO2 electroreduction to C2+ products under acidic conditions

The electrocatalytic CO 2 reduction reaction (eCO 2 RR) is a promising technology that utilizes renewable energy to convert CO 2 into value-added chemicals or fuels. Currently, most eCO 2 RR is conducted in alkaline electrolytes to activate CO 2 molecules, reduce the reduction overpotential, and suppress the competing hydrogen evolution reaction (HER). However, the alkaline electrolyte inevitably reacts with CO 2 gas to form carbonate byproducts, which lower CO 2 utilization and lead to salt precipitation, thereby compromising efficiency and stability. Acidic electrolyte offers a feasible solution to these issues by enhancing both carbon and energy efficiencies. Moreover, researchers favor multicarbon (C 2+ ) products due to their high energy densities and market values. However, achieving eCO 2 RR to C 2+ products under acidic conditions remains challenging, primarily due to the competing HER, C−C coupling barrier, and catalyst stability concerns. A comprehensive and timely overview of this field is currently lacking. This review integrates recent advances in catalyst design for CO 2 electroreduction to C 2+ products under acidic conditions. We discuss the three aforementioned issues individually, with an emphasis on advanced examples and underlying reaction mechanisms. It will focus on strategies to suppress the HER, promote C−C coupling, and enhance catalyst stability, aiming to provide effective guidance toward catalysts design in acidic eCO 2 RR to C 2+ products. Finally, we outline current challenges and future directions for acidic eCO 2 RR technologies.