Facile Synthesis of Medium‐Entropy Metal Sulfides as High‐Efficiency Electrocatalysts toward Oxygen Evolution Reaction

Abstract Developing highly efficient and durable electrocatalysts toward oxygen evolution reaction (OER) is an urgent demand to produce clean hydrogen energy. In this study, a series of medium‐entropy metal sulfides (MEMS) of (NiFeCoX) 3 S 4 (where X = Mn, Cr, Zn) are synthesized by a facile one‐pot solvothermal strategy using molecular precursors. Benefiting from the multiple‐metal synergistic effect and the low crystallinity, these MEMS show significantly enhanced electrocatalytic OER activity compared with the binary‐metal (NiFe) 3 S 4 and ternary‐metal (NiFeCo) 3 S 4 counterparts. Especially, (NiFeCoMn) 3 S 4 delivers a low overpotential of 289 mV at 10 mA cm −2 , a decent Tafel slope of 75.6 mV dec −1 and robust catalytic stability in alkaline medium, outperforming the costly IrO 2 benchmark electrocatalyst and the majority of the reported metal sulfide‐based electrocatalysts until now. These MEMS with facile synthesis and excellent electrocatalytic performance bring a great opportunity to design desirable electrocatalysts for practical application.