Bulk OsO₂ Single Crystals: Superior Catalysts for Water Oxidation

Although rutile RuO₂ has been a well-known and almost the best oxygen evolution reaction (OER) catalyst, the OER properties for the similar rutile oxide OsO₂ with the same group element with Ru have been unknown, mainly due to long-standing synthesis difficulties. In this work, we report the successful synthesis of high-quality OsO₂ single crystals, and the ground micrometer-size single crystals are chemically stable in alkaline solutions and exhibit robust OER performance. In sharp contrast, OsO₂ nanopowder reacts quickly with KOH solutions and cannot work for OER. Compared with commercial RuO₂ nanopowder, the OsO₂ single crystals show comparable catalytic current densities, remarkably lower overpotentials at high current densities and better stability. These findings question the universal applicability of nanoscaling and highlight crystal integrity as a key descriptor for achieving stable and efficient OER electrocatalysis.