Interface engineering of oxygen-vacancy-rich NiCo2O4/NiCoP heterostructure as an efficient bifunctional electrocatalyst for overall water splitting

Inexpensive bifunctional electrocatalysts towards oxygen evolution reaction (OER) and hydrogen evolution reaction (HER) is highly desirable from the perspective of energy conversion. Herein, we report a novel and high-efficiency bifunctional electrocatalyst via interface engineering within the NiCo2O4/NiCoP heterostructure. Such an interface-modulated strategy can significantly facilitate the generation of rich oxygen vacancies and enrich the active sites at the boundary of the prepared NiCo2O4/NiCoP heterostructure, leading to favorable electronic structure and fast charge-transfer capacity. For the OER, the NiCo2O4/NiCoP heterostructure exhibits an extremely low overpotential of about 295 mV at 10 mA cm−2, which is much better than that of pristine counterparts. Impressively, a low overpotential of about 198 mV at 10 mA cm−2 can meet the requirement for HER for this heterostructure in alkaline media. Furthermore, overall water-splitting can be realized through the functioning of the NiCo2O4/NiCoP heterostructure as the cathode and anode simultaneously with a cell voltage of only 1.66 V to achieve 10 mA cm−2. This work provides a promising interface-regulated strategy to realize the transition metal heterostructure as an efficient electrocatalyst in energy-related applications.