In situ chloride-mediated synthesis of TiO2 thin film photoanode with enhanced photoelectrochemical activity for carbamazepine oxidation coupled with simultaneous cathodic H2 production and CO2 conversion to fuels

Highlights: • Chloride-mediated TiO₂ photoanodes prepared by hydrothermal reaction followed by calcination. • Crystallinity, anatase/rutile ratio and surface oxygen vacancies were optimized. • The 0.1CTO-450 photoanode favored electron–hole generation and migration. • CBZ degradation and syngas production via the PEC process were enhanced. This study investigated the simultaneous photoelectrochemical (PEC) degradation of carbamazepine (CBZ), reduction of CO₂ and production of H₂ using a TiO₂ thin film as photoanode and Ag plate as cathode. The photoanode was fabricated using sequential hydrothermal and calcination processes. The use of chloride during the hydrothermal process enhanced formation of oxygen vacancies and defects on the TiO₂ surface. Calcination not only further strengthened those features but also enhanced the crystallinity and anatase/rutile ratio, endowing the TiO₂ photoanode with superior PEC capacity. Characterization of physicochemical and PEC properties revealed that photogenerated electrons-holes were rapidly generated and efficiently separated on the TiO₂ surface during the PEC process. Hydroxyl radicals were the main active species responsible for anodic oxidation of carbamazepine, while hydrogen radicals and carbon dioxide radical anions mediated CO₂ reduction and H₂ production in the cathodic process. This work confirms the suitability of the prepared TiO₂ photoanode for PEC degradation of organic pollutants coupled with CO₂ reduction and H₂ production.