Ruthenium‐Titania Interface‐Mediated Water Activation for High Turnover Frequency in Alkaline Hydrogen Evolution

ABSTRACT While heterostructured catalysts are reported to significantly improve alkaline hydrogen evolution reaction (HER) by lowering energy barriers for water dissociation, a comprehensive understanding of the interfacial mechanisms underlying their catalytic activity remains lacking. Herein, we combine in situ shell‐isolated nanoparticle‐enhanced Raman spectroscopy (SHINERS) and density functional theory (DFT) calculations to elucidate the HER mechanism of the heterostructured RuO ₂ /TiO ₂ catalyst. The RuO ₂ nanoparticles (~2 nm) are successfully deposited onto 25 nm TiO ₂ supports, forming a heterointerface that significantly enhances HER activity. RuO ₂ /TiO ₂ exhibits a remarkably low overpotential of 6.6 mV at 10 mA cm ^–2 and a Tafel slope of 36.7 mV dec ^–1 in 1 M KOH, with an impressively high turnover frequency of 25.07 s ^–1 at 100 mV. In situ SHINERS analysis reveals dynamic changes in interfacial water and adsorbates during HER, confirming the involvement of active water species in the water dissociation process in the presence of Ti—OH groups on reduced titania. DFT calculations show a lowered energy barrier for water dissociation, attributed to water activation by reduced titania and electronic interactions at the heterostructure interface. This study deepens the understanding of metal oxide functionality in heterostructured electrocatalysts and contributes to the rational design of efficient HER systems.