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

This work systematically studied thermocatalytic and photocatalytic pathways of formaldehyde degradation and H-assisted O reduction over a Pt/anatase-TiO(101) composite via DFT calculations together with constrained molecular dynamics (MD) simulations. We show that photocatalytic O reduction on Pt/TiO can directly generate OH radicals (*O → *OOH → OH) via two hydrogenation steps with small barriers, and the product selectivity (*HO or OH) is decided by the relative position between catalyst Fermi level and OH/*HO 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 + ), can always drive the direct OH generation. The additional portion of -triggered OH radicals are prone to diffuse into solution or the TiO surface and furthermore cooperate with the conventional -driven photooxidations.