Decoupling H‑Release and OH^- Management at Pd@TiO₂ Interfaces for Efficient Alkaline Hydrogen Oxidation Reaction

Operando-level insight into catalyst degradation and reaction mechanisms is essential for progress in the alkaline hydrogen oxidation reaction (HOR). Herein, these aspects are investigated using a core-shell Pd@TiO₂/C catalyst synthesized by thermal reduction followed by atomic layer deposition. The obtained catalyst exhibits high stability and delivers a mass exchange current density (j ^0,m) of 97.5 mA mg_Pd ^-1, more than three times that of uncoated Pd/C (27.5 mA mg_Pd ^-1). Identical location transmission electron microscopy reveals a growth-detachment degradation pathway for Pd/C during accelerated durability testing, whereas the TiO₂ shell in Pd@TiO₂/C effectively suppresses this degradation, resulting in enhanced structural stability. Operando X-ray absorption spectroscopy under device-relevant conditions demonstrates the complementary functions of the two components: hydrogen dissociates and forms PdH _x on the Pd core, lowering its Fermi level and driving electron transfer from TiO₂ to Pd, while the TiO₂ shell facilitates hydrogen desorption and provides OH^- adsorption sites, thereby accelerating the reaction kinetics. These findings elucidate the dual stabilizing and catalytic roles of TiO₂ and suggest a promising strategy for the design of durable and efficient alkaline HOR catalysts.