P-Doped NiMoO4 parallel arrays anchored on cobalt carbonate hydroxide with oxygen vacancies and mass transfer channels for supercapacitors and oxygen evolution

Abstract

Proper morphology design and surface dopant/vacancy engineering can effectively enlarge the exposed active surface and improve the intrinsic activity of electrodes. Herein, three-dimensional P-doped NiMoO₄ (NiMoP) parallel nanosheets anchored on cobalt carbonate hydroxide (CoCH) nanowire arrays were fabricated. The phosphorization process could also introduce oxygen vacancies on the nanosheet surface. The parallel nanosheets with quasi one-dimensional channels could facilitate electrolyte/gas mass transfer and enlarge the exposed surface, thus avoiding the “dead volume” inside the hierarchical architecture. The phosphate dopant and oxygen vacancy-rich surface could increase the intrinsic electron conductivity and create sufficient active defects. Therefore, the NiMoP@CoCH/CC electrode achieved high areal capacitance (4.00 F cm⁻² at 1 mA cm⁻²), superior rate capability (62.5% capacitance retention from 1 to 50 mA cm⁻²) and excellent stability (98.75% capacitance retention after 5000 cycles) in a three-electrode system. In addition, the as-prepared electrode also exhibited good electrocatalytic oxygen evolution activity in an alkaline solution (overpotential of 267 mV at 40 mA cm⁻²).