Heterostructured nickel/vanadium nitrides composites for efficient electrocatalytic hydrogen evolution in neutral medium

Water electrolysis capable of working in a neutral medium is compatible with direct seawater splitting, solar-driven water splitting cells, and hybrid inorganic–biological systems for renewable energy conversion and storage. Non-precious electrocatalysts for efficient and durable hydrogen evolution reactions (HER) are of paramount significance. Herein, we report that the heterostructured nitrides composites that are made of poor HER electrocatalysts of Ni₃N and VN show remarkable activity and durability for HER in a neutral medium. Ni₃N-VN composite rivals the state-of-the-art Pt/C electrocatalyst, requiring an overpotential of only 85 mV to deliver a benchmark current density of 10 mA cm⁻² in 1.0 M phosphate-buffered saline. The HER kinetics are significantly promoted in comparison with Ni₃N and VN, showing 6–17 times higher current densities and lowered Tafel slopes (73 mV decade for Ni₃N-VN and >120 mV decade⁻¹ for Ni₃N and VN). The promoted kinetics is ascribed to the interfacial heterostructures, where the electronic structures are tailored for optimal hydrogen absorption and promoted water adsorption and dissociation. This research demonstrates a powerful interfacial engineering strategy in promoting the sluggish kinetics of nitrides for HER in a neutral medium, which deserves further attention to electrocatalysts in other reactions.