P-doped cobalt carbonate hydroxide@NiMoO4 double-shelled hierarchical nanoarrays anchored on nickel foam as a bi-functional electrode for energy storage and conversion.

The rational structure design and controllable surface modification of electrode materials plays a decisive role in constructing high performance energy storage and conversion devices. Herein, the P-doped cobalt carbonate hydroxide@NiMoO4 (P-CoCH@NiMoO4) nanowires@nanosheets double-shell hierarchical structure is successfully fabricated on nickel foam. The unique nanowire@nanosheet structure with gradient porous distribution and hydrophilic nature can facilitate both the charge and electron transfer based on the synergetic effects with conductive NiMoO4 array. Importantly, the dopant of P element can enrich oxygen vacancies on the surface of CoCH nanowire, thus increase the effective active sites and enhance the electrocatalytic performance. Therefore, when act as the supercapacitor electrode, the bi-functional P-CoCH@NiMoO4/NF material achieves high areal capacitance (5.08 F cm-2 at 2 mA cm-2, 0.75 mAh cm-2) and good cyclic stability (82.7% capacitance retention after 2000 cycles). Meanwhile, when utilize as the hydrogen evolution electrode in alkaline solution, a low overpotential (115 mV at 10 mA cm-2) and Tafel slope (113.5 mV dec-1) can also be achieved.