Heterointerface engineering of Ni/Ni₃N hierarchical nanoarrays for efficient alkaline hydrogen evolution

Ni-based transition metal nitrides (TMNs) have been regarded as promising substitutes for noble-metal electrocatalysts towards the hydrogen evolution reaction (HER) due to their low cost, excellent chemical stability, high electronic conductivity, and unique electronic structure. However, facile green synthesis and rational microstructure design of Ni-based TMNs electrocatalysts with high HER activity remain challenging. In this work, we report the fabrication of Ni/Ni₃N heterostructure nanoarrays on carbon paper via a one-step magnetron sputtering method under low temperature and N₂ atmosphere. The Ni/Ni₃N hierarchical nanoarrays exhibit an excellent HER catalytic activity with a low overpotential of 37 mV at 10 mA·cm⁻² and robust long-term durability over 100 h. Furthermore, the Ni/Ni₃N||NiFeOH (NiFeOH = NiFe bimetallic hydroxide) electrolyzer requires a small voltage of 1.54 V to obtain 10 mA·cm⁻² for water electrolysis. Density functional theory (DFT) calculations reveal that the heterointerface between Ni and Ni₃N could directly induce electron redistribution to optimize the electronic structure, which accelerates the dissociation of water molecules and the subsequent hydrogen desorption, and thus boosting the HER kinetics.