In-situ formed NiS/Ni coupled interface for efficient oxygen evolution and hydrogen evolution

High-performance electrocatalysts for water splitting are desired due to the urgent requirement of clean and sustainable hydrogen production. To reduce the energy barrier, herein, we adopt a facile in-situ surface modification strategy to develop a low-cost and efficient electrocatalyst for water splitting. The synthesized mulberry-like NiS/Ni nanoparticles exhibit excellent catalytic performance for water splitting. Small overpotentials of 301 and 161 mV are needed to drive the current density of 10 mA cm−2 accompanying with remarkably low Tafel slopes of 46 and 74 mV dec−1 for oxygen evolution reaction (OER) and hydrogen evolution reaction (HER), respectively. Meanwhile, a robust electrochemical stability is demonstrated. Further high-resolution X-ray photoelectron spectroscopy analyses reveal that the intrinsic HER activity improvement is attributed to the electron-enriched S on the strongly coupled NiS and Ni interface, which simultaneously facilitates the important electron transfer, consistent with the electrochemical impedance results. The post characterizations demonstrate that surface reconstructed oxyhydroxide contributes to the OER activity and NiS/Ni is an OER precatalyst. This structure construction with in-situ formation of active interface provides an effective way to design efficient electrocatalysts for energy conversion.