Constructing S-deficient nickel sulfide/N-doped carbon interface for improved water splitting activity.

Transition-metal sulfides are an intriguing family of electrocatalysts, yet their water-splitting applications are severely hampered by uncontrollable phase reconstruction and unsatisfactory in-service durability. Herein, we developed an efficient method to construct nickel sulfide (NiS) nanoarrays on foam nickel (NF) while being protected by highly N-doped formamide-derived carbon (termed NiS-NC@NF). The NiS nanocrystals were transformed in situ from highly dispersed Ni-N-C deposited on NF, ensuring a strong coupling effect that tunes the surface properties of NiS nanocrystals via the in situ constructed NiS/N-doped carbon interface. Electrochemical measurements reveal that very low overpotentials of 88.0 and 170.0 mV ( vs. RHE) are required to achieve a current density of 10.0 mA cm -2 for hydrogen and oxygen evolution, respectively. The highly N-doped carbon matrix additionally regulates the potential-driven reconstruction of NiS in a controlled extent. Remarkably, the water electrolyzer built with NiS-NC@NF as both anode and cathode delivers an extremely low cell voltage of 1.51 V to initiate water splitting in the alkaline medium.