Oxygen‐Coordinated Nickel Single Atoms Couple Photohole Capture With C–H Cleavage in Photoelectrocatalytic Glycerol‐to‐Dihydroxyacetone Conversion

Selective photoelectrochemical oxidation of glycerol to dihydroxyacetone (DHA) requires photogenerated holes to reach the substrate faster than they drive oxygen evolution, followed by C–H cleavage without C–C fragmentation. Here, oxygen‐coordinated Ni single atoms on the TiO 2 (001) nanosheet arrays regulate both steps. Isopropanol‐probe and in situ glycerol spectra support Ni‐promoted dissociative adsorption through the secondary hydroxyl group. Radical spectroscopy and interfacial kinetics support subsequent oxidation through glycerol‐derived alkoxy species, accompanied by a 15–20‐fold acceleration of glycerol‐coupled hole transfer and suppressed oxygen evolution. Product‐based glycerol isotope effects supported the kinetic involvement of central C–H cleavage in DHA formation, while calculations showed that Ni coordination increased the energetic preference for C–H over C–C cleavage from 0.05 to 0.38 eV. Operando spectroscopy and weaker DHA adsorption support retention of the three‐carbon skeleton and product release. Under charge‐normalized conditions, the Ni single‐atom photoanode achieved a DHA Faradaic efficiency of approximately 66.6%, compared with 22.2% for unmodified TiO 2 and 16.4% for the NiO x control. DHA‐selective charge utilization persisted in recirculating‐flow operation with 0.5 M glycerol. These results support coupled control over substrate adsorption and subsequent bond selectivity as a design principle for selective PEC polyol oxidation.