Fluorine-anion engineering endows superior bifunctional activity of nickel sulfide/phosphide heterostructure for overall water splitting.

Designing advanced transition metal-based materials for electrocatalytic water splitting is of significance, but their wide application is still limited due to the lack of an effective regulation strategy. Herein, a synergistic regulation strategy of surface/interface is developed to optimize the catalytic activity of nickel sulfide (NiS). The construction of nickel phosphide with NiS heterostructure by using fluorine (F)-anion modification is successfully developed on nickel foam (F-NiP/NiS-NF) via a simple fluorination and phosphating treatment. This new kind of electrocatalyst contains plenty of active sites and strong electronic interactions, presenting superior bifunctional activity for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). The overpotentials only need 182 mV and 370 mV to reach the current density of 100 mA cm for HER and OER, respectively. In addition, the F-NiP/NiS-NF-based electrolyzer delivers promising performance for overall water splitting. A low potential of 1.55 V and 1.7 V can be achieved at the current density of 10 mA cm and 50 mA cm. This work provides a new surface/interface regulation strategy for high-efficient bifunctional electrocatalysts.