Pd0 and oxygen vacancy interfacial synergy regulates charge transfer and oxygen activation for photocatalytic oxidation of gaseous toluene

Pd nanoparticles and oxygen vacancies were co-constructed onto anatase TiO 2 . • Pd-TiO 2-x achieved 98.62% toluene removal and 84.3% mineralization. • Pd sites promoted electron transfer while oxygen vacancies activated O 2 . • Interfacial coupling enhanced reactive charge utilization and ROS generation. • Pd-TiO 2-x retained over 98% toluene removal after five cycles. The efficient photocatalytic removal of gaseous toluene over TiO 2 is hindered by rapid charge-carrier recombination, inefficient interfacial charge utilization, and limited surface oxygen activation. In this study, Pd nanoparticles and oxygen-vacancy-related defects were simultaneously introduced onto anatase TiO 2 through a one-step NaBH 4 reduction strategy. Pd, TiO 2 , TiO 2-x , and Pd-TiO 2-x were examined to distinguish the respective roles of Pd sites, defect-associated sites, and their coupled interface. Pd-TiO 2-x exhibited an actual Pd loading of 0.948 wt%, with Pd predominantly present in metallic Pd 0 state. Compared with TiO 2-x , Pd-TiO 2-x exhibited a higher concentration of oxygen vacancies and a lower interfacial charge-transfer resistance. Under UV light irradiation, Pd-TiO 2-x achieved a toluene degradation efficiency of 98.62% and a mineralization efficiency of 84.30% after 120 min, with an apparent pseudo-first-order rate constant of 0.06282 min −1 . Notably, despite exhibiting the lowest transient photocurrent among TiO 2 -based catalysts, Pd-TiO 2-x showed the highest photocatalytic activity. This non-parallel behavior suggested that its performance advantage arose primarily from the preferential interfacial migration and reactive utilization of photogenerated charge carriers, rather than from an increase in measurable charge output. Mechanistic analyses indicated that Pd 0 -rich sites promoted electron acceptance and transfer, whereas oxygen-vacancy-related sites facilitated O 2 adsorption and activation, thereby promoting the formation of • O 2 ⁻ and • OH. These results highlighted the reactive utilization of interfacial charges as an important factor governing toluene photocatalytic oxidation. Download: Download high-res image (153KB) Download: Download full-size image