Fe3O4-Based Electrocatalysts for the Oxygen Evolution Reaction: Mechanisms, Structural Engineering, and Perspectives

Water electrolysis driven by renewable electricity is a promising route to clean hydrogen, but the anodic oxygen evolution reaction (OER) suffers from sluggish kinetics that limit the overall efficiency. Magnetite (Fe3O4) has emerged as an attractive non-noble-metal electrocatalyst for the oxygen evolution reaction, owing to the natural abundance of iron, its mixed valence states, and an inverse-spinel framework that readily accommodates structural and compositional engineering. However, its practical application is hindered by limited intrinsic activity, insufficient accessible active sites, charge transport inferior to that of carbonaceous and metallic conductors, and structural reconstruction under operating conditions. This review summarizes recent advances in Fe3O4-based OER electrocatalysts, with emphasis on reaction mechanisms and structure–activity relationships. The adsorbate evolution mechanism and the lattice oxygen-mediated mechanism are first compared in acidic, neutral, and alkaline media. Four structural engineering strategies—heteroatom doping, heterostructure construction, coupling with conductive components or substrates, and morphology regulation—are then critically discussed in terms of their effects on active-site accessibility, intrinsic site activity, charge and mass transfer, and catalytic stability. Finally, the key challenges toward practical application are outlined, including identifying the genuine active phase and reaction pathway, regulating surface reconstruction, improving long-term durability at industrially relevant current densities, and developing scalable synthesis, offering guidance for the rational design of highly active and durable Fe3O4-based electrocatalysts.