High-Entropy Perovskite Fluorides: A New Platform for Oxygen Evolution Catalysis.

High-entropy perovskite fluorides (HEPFs) have great poten-tial in electrocatalysis that has not been realized because of the limitation of a high-temperature synthetic route and the limited understanding of high-entropy materials. The use of HEPFs in effective oxygen evolution catalysis and a feasible synthesis route for HEPFs in a boiled solution by combining a hydrothermal method with mechanochemistry are first reported here. These HEPFs consisting of cost-effective ele-ments dramatically gave excellent catalytic activity for the oxygen evolution reaction (OER) in an alkaline media. Par-ticularly, K0.8Na0.2(MgMnFeCoNi)F3 exhibited excellent OER performance with a low overpotential of 314 mV at a current density of 10 mA/cm2, much lower than that of commercial IrO2.