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

• Published in: Chemistry : a European journal Vol. 29; no. 46; pp. e202301455 - n/a
• Main Authors: Zhang, Ting, Zhou, Jinlei, Luo, Ting, Lu, Ji‐Qing, Li, Zhengquan, Weng, Xuexiang, Yang, Fa
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 15.08.2023
• Subjects: (bi)carbonate crossover; Acidic electrolyte; Alkalinity; Carbon dioxide; Catalysis; Cations; Chemical fuels; Chemical reduction; Chemistry; Clean technology; CO2 electroreduction; competitive HER; Crossovers; Electrochemistry; Electrolysis; Electrolytes; Exploitation; Fuel production; Hydrogen evolution reactions; microenvironment regulation; Microenvironments; Structural design; Structural engineering
• ISSN: 0947-6539; 1521-3765
• DOI: 10.1002/chem.202301455

Electrochemical CO2 reduction reaction (CO2RR) 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 (CO32−/HCO3−) formation and crossover due to the rapid and thermodynamically favourable reaction between hydroxide (OH−) with CO2, resulting in low carbon utilization efficiency and short‐lived catalysis. Very recently, CO2RR 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 CO2 conversion efficiency. Thus, it is a big challenge to effectively suppress HER and accelerate acidic CO2RR. In this review, we begin by summarizing the recent progress of acidic CO2 electrolysis, discussing the key factors limiting the application of acidic electrolytes. We then systematically discuss addressing strategies for acidic CO2 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 CO2 electrolysis are suggested. We believe this timely review can arouse researchers′ attention to CO2 crossover, inspire new insights to solve the “alkalinity problem” and enable CO2RR as a more sustainable technology. Currently, CO2 electroreduction (CO2RR) mainly adopt alkaline or neutral electrolytes to suppress the hydrogen evolution (HER), but with significant drawback of (bi)carbonate crossover, leading to low carbon utilization efficiency. CO2RR in acidic electrolytes can alleviate the “alkalinity problem”, but the competing HER is more kinetically favourable. Thus, it is a priority to effectively suppress HER and accelerate acidic CO2 electrolysis.