Replacement of an expensive anode electrocatalyst in proton exchange membrane water electrolysis is of great importance. Recently explored Co3O4 shows good activity and stability toward oxygen evolution reaction (OER) in acid; however, the stability is not adequately explained. Lack of such information delays the design of an acid-stable OER electrocatalyst. Here, we investigate the structural origin of cobalt dissolution by various local atomic configurations of Co3O4. Operando Raman studies and voltammetric data reveal that chemical reduction of the CoO2 intermediate accompanied by lattice oxygen loss leads to undercoordinated CoO sites, which then react with water and form an amorphous three-dimensional (3D) porous network of CoO­(OH) x , called the hydrous oxide layer (HOL). Growth of HOL mainly depends on the oxygen vacancies and near-surface OI– that impair the crystalline integrity and favor dissolution. These insights provide a fundamental relation between OER activity and stability and offer a specific guideline for the electrocatalyst design.

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This report presents the synthesis of ZnO nanorod/α-Fe2O3 composites by the hydrothermal method with different weight percentages of α-Fe2O3 nanoparticles. The as-synthesized nanorod composites were characterized by different techniques, such as X-ray diffraction (XRD), Fourier transform-infrared (FT-IR), field emission scanning electron microscopy (FE-SEM), electrochemical impedance spectroscopy (EIS), and X-ray photoelectron spectroscopy (XPS). From our results, it was found that the ZnO/α-Fe2O3 (3 wt%) nanorod composites exhibit a higher hydrogen evolution reaction (HER) activity when compared to other composites. The synergetic effect between ZnO and (3 wt%) of α-Fe2O3 nanocomposites resulted in a low onset potential of −125 mV, which can effectively produce more H2 than pure ZnO. The H2 production rate over the composite of ZnO/α-Fe2O3 (3 wt%) clearly shows a significant improvement in the photocatalytic activity in the heterojunction of the ZnO nanorods and α-Fe2O3 nanoparticles on nickel foam.