Trace Lattice S Inserted RuO₂ Flexible Nanosheets for Efficient and Long‐Term Acidic Oxygen Evolution Catalysis

Abstract Pursuing highly active and long‐term stable ruthenium (Ru) based oxygen evolution reaction (OER) catalyst for water electrolysis under acidic conditions is of great significance yet a tremendous challenge to date. To solve the problem of serious Ru corrosion in an acid medium, the trace lattice sulfur (S) inserted RuO₂ catalyst is prepared. The optimized catalyst (Ru/S NSs‐400) has shown a record stability of 600 h for the solely containing Ru (iridium‐free) nanomaterials. In the practical proton exchange membrane device, the Ru/S NSs‐400 can even sustain more than 300 h without obvious decay at the high current density of 250 mA cm⁻². The detailed investigations reveal that S doping not only changes the electronic structure of Ru via forming RuS coordination for high adsorption of reaction intermediates but also stabilizes Ru from over‐oxidation. This strategy is also effective for improving the stability of commercial Ru/C and homemade Ru‐based nanoparticles. This work offers a highly effective strategy to design high‐performance OER catalysts for water splitting and beyond.