Engineering the densities of grain boundaries within particle-assembled NiCo2O4 rods by sulfurization for effective water electrolysis

The development of low-cost, highly effective and stable electrocatalysts is the critical task in worldwide strive towards large-scale hydrogen production via water electrolysis. In this study, S-NiCo 2 O 4 nanorod arrays with well developed grain boundaries are synthesized on the surface of nickel foam by hydrothermal and vapor deposition methods. It is found that the electronic structure of metal active sites can be augmented by controlled doping with sulfur. The optimized S-NiCo 2 O 4 catalyst demonstrates an overpotential of 63 mV at 10 mA cm −2 in the hydrogen evolution reaction and 357 mV at 50 mA cm −2 in the oxygen evolution reaction. This novel synthesis method paves the way to prepare better performing bifunctional electrocatalysts for practical application in water electrolysis.