N, P co-doped NiMoOx three-dimensional nanoflower cluster-structured bifunctional electrocatalyst for efficient overall water splitting

Hydrogen production through electrocatlytic water splitting is a safe, clean and simple method to storage the excess electric energy and generate the raw material of fuel cell. It has become a research hotspot to explore transition metal catalysts for water electrolysis with high activity, stability, cheap price and easy preparation procedure. The features of active electrocatalysts usually have abundant active sites, high intrinsic activity, rapid electron transfer and strong structural stability. In this paper, a strategy combining hetero-elemental doping and interfacial engineering was employed to construct three-dimensional nanoflower cluster structures (N, P-NiMoO_x/NF) on nickel foam as bifunctional electrocatalyst for water splitting via hydrothermal method and chemical vapor deposition method. The doping of N and P elements effectively modifies the electronic structure of NiMoO_x nanomaterial to produce countless efficient active centers and accelerate the electron transfer, which results in the remarkable HER and OER activities of N, P-NiMoO_x/NF. In addition, N, P-NiMoO_x/NF has a unique three-dimensional nanoflower cluster structure, which can expose more active sites for contacting with reactants and leave abundant paths for the diffusion of bubbles to accelerate electrocatalytic water splitting. As a result, N, P-NiMoO_x/NF possessed high activity and superior stability, with overpotentials of 56.6 and 170 mV towards HER and OER at the current density of 10 mA cm⁻², respectively. Furthermore, the assembled two-electrode cell with N, P-NiMoO_x/NF electrocatalysts required only a small cell voltage of 1.54 V to drive a current density of 10 mA cm⁻² and stabilized at this current density for 113 hours.