Multivalence Driven High-Entropy Bimetallic Oxides for Acidic Water Oxidation

High-entropy materials have recently attracted much attention in diverse fields due to their tailorable compositions and unpredictable physicochemical properties. Generally, five or more metal elements occupying the same lattice sites in similar proportions are considered as a prerequisite for achieving high configuration entropy. Here we report an uncommon type of such material in V-doped RuO₂, where the number of metal elements is reduced to only two. Both Ru and V ions are found in mixed oxidation states, which endow the bimetallic oxides with five different cations. Each of these cations behaves as an individual species to contribute to the configuration entropy, which is high enough to stabilize the single phase near the half-doping level. The large ionic disorder in this high-entropy oxide leads to lattice distortion, grain refining, and an evolution from metal to semiconductor, making it a superior electrochemical catalyst toward acidic water oxidation.