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-p-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-p-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.