N, S co-doped carbon quantum dots modified TiO₂ for efficient hole extraction in photoelectrochemical water oxidation

Severe bulk charge recombination, limited light harvesting ability, and sluggish surface catalytic kinetics are still the technical drawbacks of TiO₂ photoanode for photoelectrochemical water splitting. Herein, an easy-handle hydrothermal-immersion method is adopted to prepare the nitrogen and sulfur co-doped CDs (NS-CDs) decorated TiO₂ photoanode (NS-CDs/TiO₂). With the synergistic effect of the hierarchical structure, the photocurrent of NS-CDs/TiO₂ photoanode reaches to 2.1 mA cm^-2 at 1.23 V _RHE (1.3 times of bare TiO₂). The enhancement is mainly ascribed to the drastically increased charge injection efficiency of NS-CDs/TiO₂ (95%). Additionally, the introduction of NS-CDs can simultaneously enhance light harvest efficiency to generate more carriers and promote charge transport ability to suppress electron-hole recombination. These demonstrations may supply a simple strategy for designing excellent photocatalysts for solar energy conversion related applications.