In-situ constructing of NiO/CoFe2O4 heterojunction through oxophilicity engineering for efficient water oxidation

In-situ constructing of heterojunctions is an effective way to achieve intimate interface contact, which accelerates the oxygen evolution reaction (OER) kinetics by optimizing the interfacial electronic structure between various components. Herein, we present a simple method to fabricate a novel NiO/CoFe₂O₄ (NiO/CFO) heterojunction by using Ni as the low-oxophilic dopant to induce the generation of oxygen-defective species, bringing the in-situ growth of NiO onto CoFe₂O₄. The generation of heterostructure triggers the electronic modulation at the interface, thus boosting the adsorption and dissociation of oxygen-containing intermediates during OER. Consequently, the NiO/CFO electrode requires a low overpotential of 270 mV to deliver a current density of 10 mA cm⁻² in 1 mol KOH. Additionally, a water splitting system assembled by NiO/CFO and 20 % Pt/C has been successfully constructed, showing a potential of 1.555 V at 10 mA cm⁻². This work, to some degree, provides a feasible way to synthesize in-situ heterojunctions and exploration for the catalytic mechanism which offers reference value for the rational design of high-performance spinel heterojunction OER catalysts.