Activating Hematite Nanoplates via Partial Reduction for Electrocatalytic Oxygen Reduction Reaction

For redox-active hematite (α-Fe2O3) materials, the adverse electroconductivity deeply obstructs the electrocatalytic activity. Herein, a series of iron oxides including α-Fe2O3 nanoplates, α-Fe2O3/Fe3O4 composites, and Fe3O4 material was prepared via a controllable reduction treatment on α-Fe2O3 precursor. When these iron oxides were characterized as electrocatalysts for oxygen reduction reaction (ORR), it was found that α-Fe2O3 nanoplates could be effectively activated via the reduction treatment. In particular, as the combined merits of composition optimization and electroconductivity improvement, the as-reduced composite consisting of α-Fe2O3 (49.6%) and Fe3O4 (50.4%) achieved the best activity of reaching the current density of 4.90 mA cm–2 at the potential of 0.4 V versus reversible hydrogen electrode (RHE) accompanied by a Tafel slope of 76 mV dec–1 and a high selectivity for four-electron pathway, surpassing single-phase α-Fe2O3 and Fe3O4, as well as other congeneric iron oxide composites. This high performance may offer a great potential of developing electrocatalysts with optimized composition and physicochemical properties.