Amorphous hybrid tungsten oxide–nickel hydroxide nanosheets used as a highly efficient electrocatalyst for hydrogen evolution reaction

There are more challenges for alkaline hydrogen evolution reaction (HER) via simultaneously expediting the electron-coupled water dissociation process (Volmer step) and the following electrochemical H₂ desorption (Heyrovsky step). Hybrid amorphous electrocatalysts are highly desirable for efficient hydrogen evolution from water-alkali electrolyzers due to the bifunctionality for the different elementary steps of HER and optimal interactions with water molecules and the reactive hydrogen intermediates (H_ad). Herein, the synthesis of amorphous hybrid ultrathin (tungsten oxide/nickel hydroxide) hydrate (a-[WO₃/Ni(OH)₂]·0.2H₂O) nanosheets on nickel foam (NF) for efficient alkaline HER is described. The structural and composition features of a-[WO₃/Ni(OH)₂]·0.2H₂O are characterized in detailed. The resulting a-[WO₃/Ni(OH)₂]·0.2H₂O/NF electrocatalyst with the synergistic effect of both hybrid components for the HER elementary steps shows greatly improved the activity and durability for the HER with a low overpotential of −41 and −163 mV at −10 and −500 mA·cm⁻², respectively, a Tafel slope as low as −72.9 mV·dec⁻¹, and long-term stability of continuous electrolysis for at least 150 h accompanying by inappreciable overpotential change in 1 M KOH. In the hybrid a-[WO₃/Ni(OH)₂]·0.2H₂O, Ni(OH)₂ and WO₃ moieties are separately responsible for accelerating dissociative adsorption of water and weakening H_ad adsorption strength, which is beneficial to the improvement of the alkaline HER activity.