Clarifying the Direct Generation of • OH Radicals in Photocatalytic O 2 Reduction: Theoretical Prediction Combined with Experimental Validation.

This work systematically studied thermocatalytic and photocatalytic pathways of formaldehyde degradation and H-assisted O 2 reduction over a Pt 13 /anatase-TiO 2 (101) composite via DFT calculations together with constrained molecular dynamics (MD) simulations. We show that photocatalytic O 2 reduction on Pt/TiO 2 can directly generate • OH radicals (*O 2 → *OOH → • OH) via two hydrogenation steps with small barriers, and the product selectivity (*H 2 O 2 or • OH) is decided by the relative position between catalyst Fermi level and • OH/*H 2 O 2 redox potential (theoretical determination of 0.07 V referencing to the SHE). Such a novel reaction channel was furthermore validated at the liquid-solid interface via constrained MD simulations and experimental electron paramagnetic resonance detections, and a wide range of H resources, e.g., *HCHO, *HCO, *H (H + + e - ), can always drive the direct • OH generation. The additional portion of e - -triggered • OH radicals are prone to diffuse into solution or the TiO 2 surface and furthermore cooperate with the conventional h + -driven photooxidations.