Facile electrochemical synthesis of Ni-Sb nanostructure supported on graphite as an affordable bifunctional electrocatalyst for hydrogen and oxygen evolution reactions

The design of bifunctional electrocatalysts with high activity and long-term stability is essential for water splitting systems. Herein, a binder-free and cost-effective Ni-Sb nanostructured catalyst was prepared using the one-step electrodeposition method from an organic solution, and its electrochemical characteristics for hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in an alkaline medium were studied. The optimized Ni-Sb electrode demonstrated the best electrocatalytic activity for hydrogen and oxygen evolution reactions. Benefiting from the unique morphology, super-hydrophilic properties, and the synergistic effect between Ni and Sb elements, low overpotentials of 158 mV and 367 mV are needed to produce a current density of 10 mA.cm(-2) for HER and OER, respectively. Noteworthy, the Ni-Sb bifunctional catalyst displayed enhanced electrocatalytic stability at a current density of 100 mA.cm(-2) and works for 60,000 s. Our experimental data based on the electrochemical impedance spectroscopy (EIS) measurements before and after the stability test confirmed that the optimized electrode retains its catalytic performances for HER and OER owing to high conductivity and fast charge transfer. This study thus provides helpful avenues to design new antimonide-based catalysts for various applications.