Two-dimensional medium-entropy NiCoFeMo MOF as a high-performance bifunctional electrocatalyst for overall water splitting

Metal-organic frameworks (MOFs) are generally considered as attractive precursors to fabricate metal compound/carbon hybrid in the electrocatalysis field. However, applying multi-metallic MOFs as direct electrocatalysts have received limited attention. In this study, a two-dimensional medium-entropy quaternary MOF (NiCoFeMo-MOF) and comparative ternary MOF (NiCoFe-MOF, NiCoMo-MOF, and NiFeMo-MOF) materials are successfully fabricated via a one-step room-temperature ultrasonication method. These MOFs all exhibit a sheet-like morphology with homogeneous elemental distribution. Electrochemical results demonstrate that quaternary NiCoFeMo-MOF shows more superior oxygen evolution reaction (OER) performance compared to the other ternary MOFs and commercial RuO 2 catalysts. The performance enhancement primarily stems from the electronic synergy within the multi-metal system, in which Ni site forms a local electronic environment that is favorable for stabilizing the *OOH intermediate, thereby effectively reducing the reaction barrier for OER. Furthermore, NiCoFeMo-MOF also displays excellent hydrogen evolution reaction (HER) activity at high current densities, and the overall water-splitting electrolyzer assembled with NiCoFeMo-MOF outperforms the corresponding commercial Pt/C||RuO 2 system. This work provides a feasible route for the facile preparation of medium entropy MOF materials and opens a new pathway for developing advanced non-noble-metal electrocatalytic materials.