Efficient electrocatalyst for solar-driven electrolytic water splitting: Phosphorus (P) and niobium (Nb) co-doped NiFe2O4 nanosheet

In the context of hydrogen production through water electrolysis, the development of efficient and stable electrocatalysts is of paramount importance. However, the creation of cost-effective electrocatalysts poses a significant challenge. In this study, a P and Nb co-doped NiFe2O4 nanosheet is designed and grown on Fe foam (referred to as P, Nb-NiFe2O4/FF). The P, Nb-NiFe2O4/FF exhibits a distinctive crystalline/amorphous heterostructure, and the co-doping of P and Nb in the material leads to the exposure of additional catalytic active sites, optimization of the electronic structure, and enhancement of charge conductivity. Additionally, the P, Nb-NiFe2O4/FF possesses a superhydrophilic surface for the enhancement of charge/mass transfer at interface and a superaerophobic surface, facilitating the efficient release of gas. The P, Nb-NiFe2O4/FF demonstrates remarkable oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) activities, achieving overpotential as low as 247 mV and 127 mV, respectively, to attain the current density response of 100 mA cm-2. Based on the high bifunctional activities, the P, Nb-NiFe2O4/FF requires only a working voltage of 1.56 V to obtain the current density of 10 mA cm-2 in overall water splitting. Furthermore, the overall water splitting device of P, Nb-NiFe2O4/FF is integrated with a commercial solar cell to simulate a solar-powered water splitting system, resulting in as superior solar-to-hydrogen conversion efficiency of 15.11%.