Catalyst–electrolyte interface engineering propels progress in acidic CO2 electroreduction

Abstract

The electrocatalytic carbon dioxide reduction reaction (CO₂RR) is a viable strategy that supports carbon neutrality via transforming the dominant greenhouse gas CO₂ into high-value-added chemicals. The CO₂RR in alkaline and neutral media has thrived in recent years owing to their high CO₂ solubility and favourable CO₂ activation ability. However, critical challenges have emerged, such as carbonate formation and subsequent CO₂ crossover to the anodic sides, which decreases the carbon efficiency and stability of the system. Alternatively, acidic media provide an advantageous environment to prevent CO₂ crossover into the anolyte but suffers from strong HER competition, which is significantly more active under acidic conditions, largely reducing the CO₂ conversion efficiency. Research on acidic CO₂RRs began with some basic studies, including testing various catalysts and electrolytes and designing diverse substrate structures. With advancements in characterization technologies, it has been found that the acidic CO₂RR is not only influenced by variations in the composition of the catalyst, substrate or electrolyte, but also by internal changes at the catalyst–electrolyte interface. Thus, catalyst–electrolyte interface engineering, involving electrolyte engineering, catalyst modification, and interface optimization, provides many feasible solutions for acidic CO₂RRs to weaken the competing HER. Importantly, it extends acidic CO₂RR investigation to the exploration of electronic structures, interfacial adsorption of cations and anions, and surface hydrophobicity of catalysts in the presence of an electric field. However, there are limited articles reviewing acidic CO₂RRs from this perspective, and thus, this review aims to discuss the challenges, history, evaluation, and breakthroughs in acidic CO₂RRs regarding catalyst–electrolyte interface engineering, thereby providing insights for the future development of acidic CO₂RRs.