Platinum Single Atoms Strongly Promote Superoxide Formation in Titania-Based Photocatalysis – Platinum Nanoparticles Don't

The selective reduction of molecular oxygen to superoxide is one of the key reactions in electrochemistry and photocatalysis. Here the effect of Pt co-catalysts, dispersed on titania, either as single atoms or as nanoparticles, on the photocatalytic superoxide (^•O₂⁻) formation in O₂ containing solutions is investigated. The ^•O₂⁻ formation is traced by nitroblue tetrazolium (NBT) assays and in detail by EPR measurements using TEMPO as ^•O₂⁻ radical scavenger. The results show that the photocatalytic formation rate of ^•O₂⁻ on titania can strongly be enhanced by using Pt single atoms as a co-catalyst, whereas Pt nanoparticles hardly exhibit any accelerating effect. This finding is of considerable significance regarding photocatalytic degradation and photocatalytic oxidative synthesis processes.