Self-assembled Plasmonic Au-TiO2 Supraparticles for Enhanced Photocatalytic Hydrogen Peroxide Generation

Plasmonic nanoparticles deposited on semiconductors have shown great promise in photocatalysis. In the present study, we demonstrate the synthesis of Au-TiO2 supraparticles by self-assembly, leading to collective plasmonic excitation as an effective strategy to enhance the plasmon energy transfer to TiO2. Au-TiO2 supraparticles are synthesized via electrostatic interaction between poly(allylamine hydrochloride)-coated Au nanoparticles and titanium bis(ammonium lactate) dihydroxide (TALH) as the titania precursor. The suprastructure size and density are controlled by varying the amount of TALH in the Au@polymer matrix. The use of large, dense supraparticles (500 nm – 50 µm) enables to double the hydrogen peroxide yield compared to small supraparticles (100 nm – 5 µm). Our mechanistic investigation points at a pivotal role of a strongly increased near-electric field enhancement and associated hot electrons that partake in the reaction. Radical quenching experiments and EPR spectroscopy further confirm the importance of an electron-transfer-based O2-reduction pathway at the root of the enhanced photocatalytic H2O2 production.