Plasma-Induced Defect Engineering and Cation Refilling of NiMoO4 Parallel Arrays for Overall Water Splitting.

Developing highly active water splitting electrocatalysts with ordered micro/nanostructures and uniformly distributed active sites can meet the increasing requirement for sustainable energy storage/utilization technologies. However, the stability of complicated structures and active sites during a long-term process is also a challenge. Herein, we fabricate a novel approach to create sufficient atomic defects via N2 plasma treatment onto parallel aligned NiMoO4 nanosheets, followed by refilling of these defects via heterocation dopants and stabilizing them by annealing. The parallel aligned nanosheet arrays with an open structure and quasi-two-dimensional long-range diffusion channels can accelerate the mass transfer at the electrolyte/gas interface, while the incorporation of Fe/Pt atoms into defect sites can modulate the local electronic environment and facilitate the adsorption/reaction kinetics. The optimized Pt-NP-NMC/CC-5 and Fe-NP-NMC/CC-10 electrodes exhibit low overpotentials of 71 and 241 mV at 10 mA cm-2 for the hydrogen evolution reaction (HER) and the oxygen evolution reaction (OER), respectively, and the assembled device reveals a low voltage of 1.55 V for overall water splitting. This plasma-induced high-efficiency defect engineering and coupled active site stabilization strategy can be extended to large-scale fabrication of high-end electrocatalysts.