Oxygen-modified Ru for efficient alkaline hydrogen evolution reaction

Ruthenium (Ru) is considered a highly promising catalyst for the hydrogen evolution reaction (HER) because of its similar d-band center to platinum and more affordable price. However, the catalytic activities of Ru-based materials remain insufficient for large-scale water electrolysis. In this work, we report that an oxygen-modified Ru catalyst (Ru/C-220) can achieve superior catalytic performance for the HER with an overpotential of 18 mV at 10 mA cm^-2, a Tafel slope of 34.9 mV dec^-1, and around five-fold increase in mass activity at an overpotential of 100 mV compared to the unannealed catalyst. XPS characterization reveals that the catalyst, after air annealing, exhibits a higher content of lattice-O^2- and tetravalent ruthenium (Ru⁴⁺), which are key factors contributing to performance enhancement. The underpotential-deposited hydrogen (H_upd) tests and density-functional-theory (DFT) calculations further validate that the enhanced performance of Ru/C-220 stems from oxygen modification, which reduces and optimizes the *H adsorption energy at the Ru active sites. Anion exchange membrane water electrolysis (AEMWE) tests confirm the application potential of the oxygen-modified Ru.