Modulation of strong metal support interaction of IrO_x/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 IrO_x under OER conditions. Such reconstructed IrO_x contains labile lattice oxygen that can participate in the OER, leading to structural degradation and poor durability. In this study, a supported IrO_x@TiO₂ catalyst was synthesized via a high-temperature shock (HTS) strategy, which enabled effective control over the IrO_x particle size and simultaneously promoted intimate IrO_x-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 IrO_x@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.