Modulation of strong metal support interaction of IrOx/TiO2 for acidic oxygen evolution reaction.

Proton exchange membrane water electrolysis (PEMWE) is a promising technology for large-scale green hydrogen production. However, acidic oxygen evolution reaction (OER) catalysts still suffer from an intrinsic trade-off between high catalytic activity and long term structural stability. Crystalline IrO2 exhibits relatively good stability but limited intrinsic activity, whereas metallic or low-valence Ir species usually show high initial activity but undergo oxidative reconstruction into highly oxidized amorphous IrOx under OER conditions. Such reconstructed IrOx contains labile lattice oxygen that can participate in the OER, leading to structural degradation and poor durability. In this study, a supported IrOx@TiO2 catalyst was synthesized via a high-temperature shock (HTS) strategy, which enabled effective control over the IrOx particle size and simultaneously promoted intimate IrOx-TiO2 interfacial coupling. The electronic coupling at the Ir-O-Ti interface modulated the electronic structure of Ir active sites, suppressed lattice oxygen participation during OER, and favored a predominantly adsorbate evolution mechanism (AEM) pathway, thereby enhancing catalyst stability. In 0.5 M H2SO4 electrolyte, the IrOx@TiO2 catalyst achieved a current density of 10 mA cm-2 with an overpotential of only 254 mV and a mass activity of 317.6 A g-1, which was 10.6 times higher than that of commercial IrO2. Additionally, the catalyst demonstrated excellent long-term stability, maintaining continuous operation for over 600 h with significantly improved durability. The reduced involvement of lattice oxygen and the enhanced adsorbate-mediated OER behavior were supported by 18O-labeled differential electrochemical mass spectrometry (DEMS) and in situ Fourier transform infrared spectroscopy (FTIR). This study demonstrates that the Ir-O-Ti interfacial interaction can suppress lattice oxygen participation during acidic OER and promote an AEM-dominated reaction pathway by modulating the electronic state of active sites, providing a new strategy to overcome the activity-stability trade-off in acidic OER catalysts.