Active-site modulation of nickel molybdate for efficient electrocatalytic water splitting

The development of efficient non-precious electrocatalysts is crucial for the practical application of water splitting. Herein, improving the catalytic active sites of non-precious electrocatalysts for sluggish anodic oxygen evolution reaction (OER) is currently urgent to address. In this work, a strategy combining electronic structure modulation with surface reconstruction is proposed to enhance the active sites of nickel molybdate (NiMoO₄) as an effective electrocatalyst for OER. By self-diffusion of phosphorus (P) on NiMoO₄, the synthesized P_0.79-NMO/NF possesses an overpotential of 280 mV at 10 mA cm^-2, which is lower than that of IrO₂ electrocatalyst (343 mV) in alkaline solution. For water splitting performance, the P_0.79-NMO/NF || Pt/Ti electrodes require only a cell voltage of 1.83 V to achieve 10 mA cm^-2, which is lower than that of IrO₂ || Pt/Ti (1.94 V). The density functional theory (DFT) calculation results suggest that the enhanced OER performance is due to the tuned electronic structure of active sites by P doping, which contributes to a weak binding strength for intermediates. The experimental results also found that P doping could promote the generation of NiOOH on the surface, which further increased the active sites for OER. The work inspires a facile approach to synthesize efficient non-precious metal electrocatalysts for water splitting.