aracterization of an IrO 2 – Fe 2 O 3 electrocatalyst for the hydrogen evolution reaction in acidic water electrolysis †

Water electrolysis is one of the most promising processes for a hydrogen-based economy, so the development of highly active, durable, and inexpensive catalysts for the hydrogen evolution reaction (HER) is very important. IrO2 is known to be one of the most active catalysts for the oxygen evolution reaction (OER) in a PEM electrolyzer, but the HER activity of IrO2 is rarely studied because of its low cathodic current compared to platinum. Herein, an IrO2–Fe2O3 composite oxide was prepared by a thermal decomposition method. The physical and electrochemical characterization of the material was achieved by scanning electron microscopy (SEM), X-ray fluorescence (XRF), X-ray diffraction (XRD), cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Compared to that of IrO2, the CV curves of the IrO2–Fe2O3 electrode reveal that hydrogen is more easily adsorbed on the surface, which would lead to the H underpotential deposition (H-UPD) redox current increasing significantly. Therefore, the IrO2–Fe2O3 electrode exhibits higher HER activity than that of the IrO2 electrode in 0.5 M H2SO4 solution as shown by linear sweep voltammetry (LSV). It is attributed to the electronic structure modification of IrO2 and synergetic effect between Ir and Fe in the IrO2–Fe2O3 electrode. In addition, the Tafel slope of 36.2 mV dec 1 suggests that the mechanism for the IrO2–Fe2O3-catalyzed HER is Volmer–Heyrovsky.