Unveiling wavelength-dependent roles of light in dynamic structures for photothermal toluene oxidation over atomically dispersed Pd/TiO2

Abstract

Photothermal synergistic catalysis, integrating light and heat, is an encouraging green strategy for various catalytic reactions, yet the fundamental role of light in governing activity remains unclear. Herein, using toluene oxidation as a model reaction, we investigated the light contribution at different wavelengths over an atomically dispersed Pd/H–TiO₂ catalyst and observed dynamic structural changes on Pd and TiO₂ active centers during toluene oxidation. In situ XPS and finite-difference time-domain (FDTD) simulations demonstrated two inverse electron-transfer pathways under UV and visible irradiation. Under visible light at 130 °C, high-energy hot electrons generated from Pd overcame the Schottky barrier and injected into TiO₂ via Pd–O–Ti bridges to react with TiO₂, inducing abundant oxygen vacancies. This process accelerated O₂ activation and photogenerated carrier separation, generating more ˙O₂⁻ than under UV conditions and delivering 91.1% toluene conversion and 93.6% CO₂ selectivity, comparable with UV-vis conditions and far surpassing UV conditions. Conversely, free electrons produced from TiO₂ under UV exposure transferred to Pd to increase its electron density, whereas these hardly altered the structure and reactivity of Pd/H–TiO₂, leading to approximately 7.0% toluene conversion and CO₂ yield. This work revealed the essential role of light at different wavelengths in promoting toluene degradation, guiding the design of efficient photothermal catalysts for VOC remediation.