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

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).