Engineering nanoconfined Fe-based electrocatalysts toward sustainable energy conversion

Fe-based electrocatalysts are promising alternatives to noble metals for sustainable energy conversion, but their applications are limited by the instability of Fe active centers under electrochemical conditions. Nanoconfinement engineering offers an effective strategy to regulate the formation and dynamic evolution of Fe active sites. Herein, we summarize recent advances in nanoconfined Fe-based electrocatalysts for energy conversion applications. The fundamental mechanisms of nanoconfinement are first discussed, with emphasis on structural confinement and stabilization, electronic/coordination regulation, local microenvironment modulation, and their dynamic coupling under operating conditions. Representative confinement strategies, including MOF/template-directed confinement, carbon encapsulation, coordination confinement, and heterointerface confinement, are systematically reviewed. Their roles in regulating Fe active-site structures, evolution, and catalytic functions across diverse energy conversion reactions are highlighted. Finally, current challenges and future perspectives regarding operando identification of active structures, quantitative structure-activity relationships, and scalable fabrication are proposed. This review provides mechanistic insights into the design of high-performance Fe-based electrocatalysts through nanoconfinement engineering.