Insight into charge carrier dynamics and interface design of {0 0 1} TiO2 coupled with TiOF2 for photocatalytic degradation of contaminants of emerging concern

• Highly efficient {0 0 1}TiO 2 /TiOF 2 heterojunction photocatalysts in the broad TiOF 2 content were presented. • TRMC measurements showed an increased number of photogenerated charge carriers in the heterojunction. • DFT calculations revealed high potential barriers existing within the TiOF 2 structure. • Photocatalytic generation of •OH radicals and CECs degradation in water were investigated. • Efficient interfacial charge separation was achieved at low TiOF 2 content (1.5–6 %). Herein, the role of titanium oxyfluoride (TiOF 2 ) on the charge carriers generation and electron transport in the {0 0 1} TiO 2 /TiOF 2 heterojunction photocatalysts was examined. Time-resolved microwave conductivity (TRMC), fluorescence lifetime spectroscopy, and DFT calculations were applied to investigate the charge carriers dynamics. These binary photocatalysts in a broad TiOF 2 content were further studied in photocatalytic generation of hydroxyl radicals (•OH) and degradation of several organic contaminants of emerging concern (CECs), namely 4-chlorophenol (4CP), myclobutanil (MCL) and carbamazepine (CBZ). Regardless of the CEC tested, it was found that the combination of highly-energetic {0 0 1} TiO 2 with TiOF 2 phase improved the photocatalytic activity compared to the pristine anatase. The presence of the TiOF 2 phase in the heterojunction increased the interfacial charge carriers separation and enhanced the generation of •OH radicals. Maximised photocatalytic activity and TOC reduction were observed for composites with a TiOF 2 content of 1.5 %–6 %, which exhibited the highest number of photogenerated charge carriers and a longer lifetime compared to those with higher TiOF 2 content. DFT calculations revealed high potential barriers within the TiOF 2 structure, which explains the optimum at a low level of TiOF 2 amount. Finally, high photocatalytic activity was maintained in five consecutive degradation cycles.