Nanostructured Electrocatalysts for CO 2 Conversion in Acidic Electrolytes

Electrochemical CO 2 reduction in acidic media offers an appealing route to overcome the issues related to carbonates precipitation in neutral or basic electrolytes. However, acidic conditions strongly favor the hydrogen evolution reaction, and catalysts often suffer degradation. Recent studies underscore the critical role of engineering the local environment to address these challenges. High concentrations of alkali cations in the electrolyte have demonstrated the promotion of OH − ‐rich local environment at the catalyst interface. However, their solubility limits and cost hinder large‐scale deployment. Alternatively, electrocatalysts rational design, through tailored nanostructures, has emerged as an effective strategy to establish localized alkaline microenvironments. Three main approaches have been identified: (i) space‐confined nanostructures, (ii) electronic structure modulation, and (iii) interfacial functionalization. These methods can control mass transport and tune intermediate adsorption energies, complementing other strategies and enabling high Faradaic efficiencies and long‐term stability at industrially relevant current densities in acidic media. This review summarizes these strategies, elucidates their underlying mechanisms, and outlines future directions for robust acidic CO 2 reduction, providing a coherent framework for designing efficient, selective, and durable CO 2 electrolysis systems in acidic conditions.