In Situ Reconfigured Heterostructure Active Sites on Transition Metal Sulfides Heterojunction for Accelerated Water Oxidation.

Transition metal sulfides (TMSs) are promising noble-metal-free electrocatalysts for electrochemical water splitting due to their distinctive physical and chemical properties, but they usually undergo complicated structure reconfiguration during the oxygen evolution reaction (OER). Precisely controlling the reconfiguration of TMSs for in situ generation of high-activity real active sites still remains a great challenge. Herein, we propose to in situ reconfigure heterostructure active-sites on transition metal sulfides via heterojunction engineering and achieve high OER performances on (Ni,Fe)S/MoS catalysts. The continuous leaching of Mo and S during electrooxidation induces the reconfiguration, and the strong electronic interaction of (Ni,Fe)S and MoS generates the special Ni(OH)/NiOOH/FeOOH heterostructure sites via an asynchronous reconfiguration of Fe and Ni. The (Ni,Fe)S/MoS heterostructure catalyst therefore exhibits excellent OER activity (a small overpotential of 228 mV at 100 mA cm) and a low voltage in an alkaline water electrolyzer (1.44 V at 10 mA cm), outperforming the homogeneous Mo-free NiFe sulfide catalysts with conventional reconfiguration of Ni-doped FeOOH. This work sheds light on the precise structures design under complicated electrochemical reconstruction and broadens the horizon of reconstruction chemistry to design low-cost and efficient electrocatalysts.