Enhanced photocatalytic activities of commercial P25 TiO₂ by trapping holes and transferring electrons for CO₂ conversion and 2,4-dichlorophenol degradation

Graphical abstract: TiO₂ Charge separation is enhanced by transferring electrons and trapping holes for improved photoactivities to convert CO₂ and degrade pollutant. - Highlights: • P25 TiO₂ is co-modified with chloride and phosphate anions, and then coupled with CQDs. • Photocatalytic activities for CO₂ reduction and pollutant degradation are improved. • Improved photoactivities are attributed to the enhanced charge separation. • Modified chloride and phosphate anions could effectively trap photogenerated holes. • Coupled CQDs could facilitate photogenerated electrons transfer and separation. - Abstract: In this work, commercial P25 TiO₂ was co-modified with chloride and phosphate anions by a simple impregnation method, and then coupled with carbon quantum dots with a wet-chemical process. It is demonstrated that the photocatalytic activities of P25 TiO₂ for CO₂ conversion and 2,4-dichlorophenol degradation are improved obviously after co-modifying chloride and phosphate anions and then coupling with carbon dots. It is confirmed that the modified chloride and phosphate anions could effectively trap photogenerated holes, while the coupled carbon dots could facilitate photogenerated electrons transfer based on the steady-state surface photovoltage spectra, I–V curves, the electrochemical impedance spectra and the formed ·OH amounts, implying that the photogenerated charge separation of P25 TiO₂ is greatly enhanced, leading to the obviously-improved activities. This work would help us develop a much feasible route to improve the photocatalytic activities of P25 TiO₂.