Activating Hematite Nanoplates via Partial Reduction\nfor Electrocatalytic Oxygen Reduction Reaction

Abstract

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