Interfacial hetero‐phase construction in nickel/molybdenum selenide hybrids to promote the water splitting performance

In this work, a novel hetero-phase interface structure (NiMoSe/NF-2), consisting of crystalline (NiSe) and amorphous (MoSe x ), was constructed by annealing Ni 0.85 Se/MoSe x hybrid (NiMoSe/NF-1), synthesized through hydrothermal and selenylation steps. For hydrogen evolution and oxygen evolution reaction, the NiMoSe/NF-2 exhibited an overpotential of 91 mV (10 mA cm −2 ) and 307 mV (100 mA cm −2 ) with the Tafel slope of 48.1 mV dec −1 and 30.9 mV dec −1 , respectively, superior to NiMoSe/NF-1. Meanwhile, much higher stability with 10 and 14 h tests was also respectively achieved for HER and OER. Using the NiMoSe/NF-2 as anode and cathode, the electrolyzer showed a long-time stability up to 14 h with the current density of 100 mA cm −2 at the potential of 1.91 V for overall water splitting. The density functional theory calculation validates that the crystalline/amorphous hetero-phase structure remarkably reduces the Gibbs free energy difference for both HER/OER and the increased occupation densities of electronic states near Fermi level accelerated charge transfer rate during electrocatalytic process. The hydrogen and oxygen intermediates desorption are facilitated by the downshift of Ni d-band center. The proposed crystalline/amorphous hetero-phase structure is prospective for designing bifunctional catalysts for water splitting.