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 <i>in situ</i> 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)S₂/MoS₂ catalysts. The continuous leaching of Mo and S during electrooxidation induces the reconfiguration, and the strong electronic interaction of (Ni,Fe)S₂ and MoS₂ generates the special Ni(OH)₂/NiOOH/FeOOH heterostructure sites via an asynchronous reconfiguration of Fe and Ni. The (Ni,Fe)S₂/MoS₂ heterostructure catalyst therefore exhibits excellent OER activity (a small overpotential of 228 mV at 100 mA cm^-2) and a low voltage in an alkaline water electrolyzer (1.44 V at 10 mA cm^-2), 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.