Interfacial Engineering for Acidic CO ₂ Electroreduction: Challenges and Strategies

The electrocatalytic CO 2 reduction reaction (CO 2 RR) in acidic media presents a promising route for CO 2 utilization. This approach substantially mitigates the pervasive carbonate formation issue encountered in neutral/alkaline electrolytes. However, the local alkalization at the cathode interface under high current density operation can still induce (bi)carbonate formation, while the required high ionic strength may concurrently reduce CO 2 availability via the “salting‐out” effect. These constraints impose non‐negligible limitations on carbon efficiency. The practical implementation is hindered by the predominant hydrogen evolution reaction (HER) and rapid catalyst degradation under harsh acidic conditions. This review systematically summarizes recent advances in interfacial modification strategies that address these challenges by constructing functional layers on catalyst surfaces. These approaches are categorized into two complementary pathways: microenvironment regulation and structural protection. The former focuses on suppressing proton transport, enriching alkali metal cations, and managing reactants/intermediates to create a localized reaction‐friendly environment; the latter involves building anti‐corrosion barriers, anchoring active sites, and guiding surface reconstruction to enhance catalyst durability. We further discuss the significant roles of advanced in situ/operando characterization techniques and theoretical simulations in elucidating the mechanisms of these modifications, enabling the deciphering of dynamic interfacial processes and electronic structure evolution. Finally, we outline future research directions, emphasizing the need for multifunctional integrated interfaces, improved stability under industrial conditions, and optimized electrolyzer system design. This review provides valuable insights for developing efficient, stable, and scalable acidic CO 2 RR technologies, bridging fundamental research and industrial applications.