Interface engineering and heterometal doping Mo-NiS/Ni(OH)₂ for overall water splitting

Developing cost-effective, efficient and bifunctional electrocatalysts is vital for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) application. The catalytic activity of electrocatalysts could be optimized by reasonable electronic structure regulation and increasing active sites. Herein, we report the design and fabrication of Mo-doped nickel sulfide/hydroxide heterostructures (Mo-NiS/Ni(OH)₂) as a multisite water splitting catalyst via straightforward solvothermal and in-situ growth strategy. Based on foreign metal doping and interface interaction, the electronic conductivity of heterostructures is improved and the charge transfer kinetics across the interface is promoted, which are demonstrated by the theoretical calculations. Mo-NiS/Ni(OH)₂ electrocatalyst is endowed with high electrocatalytic performance for water splitting and remarkable durability in alkaline electrolyte. It exhibits the low overpotential of 186 and 74 mV at 10 mA·cm^-2 for OER and HER, respectively. Importantly, after continuously working for 50 h, the current densities of HER and OER both show negligible degeneration. Even, the resulting Mo-NiS/Ni(OH)₂ better catalyzes water splitting, yielding a current density of 10 mA·cm^-2 at a cell voltage of 1.5 V and outperforming Pt/C-IrO₂ couple (1.53 V). This result demonstrates that transition metal doping and heterogeneous interface engineering are useful means for conventional catalyst design.