Tungsten regulated medium-entropy heterostructure as a highly efficient electrocatalyst for oxygen evolution reaction

Medium-entropy alloys (MEAs) as electrocatalysts have attracted considerable attention in the field of water splitting. However, effective modulation of MEAs to achieve highly efficient catalysis remains a challenge. Herein, we applied a metal-organic framework (MOF) templating strategy to obtain FeCoNi MEA nanoparticles with excellent oxygen evolution reaction (OER) activity and tungsten improved FeCoNi-W medium-entropy heterostructure catalysts. The incorporation of tungsten changes the electronic structure of FeCoNi MEA. The mesoporous alloy exhibits multiple active sites and unique atomic-level synergies that enhance the effective binding of reactants and the formation of crucial *OH intermediates critical for OER. The rationally designed and constructed tungsten-refined FeCoNi-W medium-entropy heterostructure electrode demonstrates superior OER performance (270 mV at 10 mA cm^-2, a Tafel slope of 43.2 mV dec^-1) and stability (50 h at 100 mA cm^-2) compared to commercial noble metal electrodes. This work will provide a basis for tailoring the properties of medium/high-entropy alloys (M/HEAs) through local chemical modification.