Synthesis and characterization of an IrO2–Fe2O3 electrocatalyst for the hydrogen evolution reaction in acidic water electrolysis

Abstract

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.