Acidic CO2 Electrolysis Addressing the “Alkalinity Issue” and Achieving High CO2 Utilization

Abstract Electrochemical CO 2 reduction reaction (CO 2 RR) provides a promising approach for sustainable chemical fuel production of carbon neutrality. Neutral and alkaline electrolytes are predominantly employed in the current electrolysis system, but with striking drawbacks of (bi)carbonate (CO 3 2− /HCO 3 − ) formation and crossover due to the rapid and thermodynamically favourable reaction between hydroxide (OH − ) with CO 2 , resulting in low carbon utilization efficiency and short‐lived catalysis. Very recently, CO 2 RR in acidic media can effectively address the (bi)carbonate issue; however, the competing hydrogen evolution reaction (HER) is more kinetically favourable in acidic electrolytes, which dramatically reduces CO 2 conversion efficiency. Thus, it is a big challenge to effectively suppress HER and accelerate acidic CO 2 RR. In this review, we begin by summarizing the recent progress of acidic CO 2 electrolysis, discussing the key factors limiting the application of acidic electrolytes. We then systematically discuss addressing strategies for acidic CO 2 electrolysis, including electrolyte microenvironment modulation, alkali cations adjusting, surface/interface functionalization, nanoconfinement structural design, and novel electrolyzer exploitation. Finally, the new challenges and perspectives of acidic CO 2 electrolysis are suggested. We believe this timely review can arouse researchers′ attention to CO 2 crossover, inspire new insights to solve the “alkalinity problem” and enable CO 2 RR as a more sustainable technology.