Influence of TiO2 electronic structure and strong metal-support interaction on plasmonic Au photocatalytic oxidations

Aiming at understanding how plasmonic reactions depend on important parameters such as metal loading and strong metal-support interaction (SMSI), we report the plasmonic photodegradation of formic acid (FA) under green LED irradiation employing three TiO2 supports (stoichiometric TiO2, N-doped TiO2, black TiO2) modified with Au nanoparticles (NPs) 3-6 nm in size. The rate of FA photo-oxidation follows different trends depending on Au loading for stoichiometric and doped Au/TiO2 materials. In the first case, the only contribution of hot electron transfer produces a volcano-shaped curve of photoreaction rates with increasing the Au loading. When TiO2 contains intra-bandgap states the photoactivity increases linearly with the Au NPs amount, thanks to the concomitant enhancement produced by hot electron transfer and plasmonic resonant energy transfer (PRET). The role of PRET is supported by Finite-Difference Time-Domain simulations, which show that the increase of both Au NPs inter-distance and of SMSI enhances the probability of charge carrier generation at the Au/TiO2 interface.