High-entropy alloy metallene for highly efficient overall water splitting in acidic media

The preparation of stable and efficient acidic overall water splitting catalysts is crucial to advance the progress of proton exchange membrane water electrolyzers. Herein, we successfully prepared IrPdRhMoW HEA metallene with rich amorphous and crystalline structures. In 0.5 mol L⁻¹ H₂SO₄, the extraordinary catalytic performance (the overpotentials for hydrogen evolution (HER) and oxygen evolution (OER) of IrPdRhMoW/C at 10 mA cm⁻² are 15 mV and 188 mV, respectively) is far stronger than that of commercial catalysts (HER: Pt/C, 47 mV and OER: RuO₂, 305 mV) and even other reported noble metal-based catalysts. Using IrPdRhMoW/C for the overall water splitting, only a cell voltage of 1.48 V is required to achieve 10 mA cm⁻² and 1.59 V required to achieve 100 mA cm⁻², which is the best voltage under high current density reported so far. More importantly, the IrPdRhMoW/C still maintains excellent electroactivity and structural stability after 100 h of water splitting at 100 mA cm⁻². Theory calculations reveal the self-balanced effect of electronic structures in the HEA due to the co-existence of crystalline and amorphous lattice structures. The strong orbital couplings not only maximize the electroactivity towards both HER and OER but also stabilize the valence states of metal sites for durable electrocatalysis.