Single-Pt-Atom-Decorated TiO₂ Nanorod Arrays for Photoelectrochemical C–H Chlorination

Photoelectrochemical (PEC) chloride oxidation reaction offers a green and sustainable approach for the synthesis of chlorinated chemicals, pesticides, pharmaceuticals/drugs, etc. However, until now, efficient PEC chloride activation remains highly challenging, primarily due to the lack of effective catalytically active reaction sites on the developed photoanodes. Herein, we construct a high-performance photoanode for PEC C-H chlorination by controllably embedding Pt single atoms onto positively charged TiO₂ nanorod arrays (denoted as Pt₁-<i>p</i>-TiO₂ NRAs). The one-dimensional single-crystalline TiO₂ nanorods not only create a rapid electron transport pathway but also orthogonalize the light absorption and hole transport directions, effectively suppressing photogenerated electron-hole recombination. Furthermore, the positively charged TiO₂ nanorod surface induced by electrochemical reduction can facilitate the anchoring of single Pt atoms as C-H chlorination active sites onto TiO₂ and at the same time modulate the charge carrier dynamics. Consequently, high selectivity (up to 87%) and Faradaic efficiency (close to 60%) toward chlorination of organics are achieved over Pt₁-<i>p</i>-TiO₂ NRAs using NaCl as the chlorine source under light illumination. PEC experiments and mechanistic investigations demonstrate that the single Pt atoms on TiO₂ nanorods can help to effectively separate photoexcited charge carriers and induce preferable chloride ions' adsorption as well as electron transfer from Pt single atoms to TiO₂ nanorods to generate reactive chloride radicals (Cl•), which play a key role in PEC C-H chlorination.