High-Entropy\nRuthenium-Based Oxides with Rich Grain\nBoundaries for Efficient Oxygen Evolution

Developing efficient and stable oxygen evolution reaction\n(OER)\nelectrocatalysts is essential for the production of hydrogen from\nwater electrolysis. Here, we successfully synthesized a high-entropy\nruthenium-based oxide (RuMnFeCoNiO-HEO) with rich grain boundaries\nusing a fast and nonequilibrium molten salt method. The RuMnFeCoNiO-HEO\nwith significantly reduced ruthenium dosage could exhibit much higher\nOER performance with a low overpotential of 190 mV at 10 mA/cm<sup>2</sup> and long-term durability of 100-h continuous operation under\n100 mA/cm<sup>2</sup> in alkaline solution. The mass activity and\nturnover frequency of RuFeCoNiMn-HEO are significantly enhanced by\nnearly 1 order of magnitude compared to those of commercial RuO<sub>2</sub>. Microstructural characterizations reveal that the incorporation\nof four extra 3d transition metals into ruthenium oxides results in\nthe formation of Ru-based high-entropy materials with a rich grain\nboundary structure and unsaturated coordination Ru active centers,\nwhich optimize both the electrocatalytic activity and electrochemical\ndurability of RuMnFeCoNiO-HEO during the OER process.