Investigation of the local photothermal effects by fabricating a CQDs/Au/TiO2 photoelectrode in a PEC water splitting system

The high efficiency of the photoanode material is of great significance for photoelectrochemical (PEC) water splitting. Herein, a CQDs/Au/TiO2 nanorod array composite photoanode was constructed with special attention to local photothermal effects. The intensity and characteristics of the local thermal effect generated by the photothermal conversion of plasmonic Au nanoparticles (Au NPs) and carbon quantum dots (CQDs) are accurately represented by an equivalent simplified temperature field model constructed innovatively. Further studies demonstrated that the local thermal effect not only stimulates the activity of the small polaron semiconductor TiO2, but also accelerates the charge transfer and surface dynamic reaction from the aspects of kinetics and thermodynamics. Simulation and experimental results also showed that the surface plasmon resonance (SPR) effect of Au NPs and the up-conversion fluorescence characteristics of CQDs can cooperate to improve the carrier concentration. Meanwhile, the formation of a Schottky heterojunction between Au and TiO2, and CQDs as hole collectors synergistically promoted the bulk charge separation. Therefore, the CQDs/Au/TiO2 photoanode achieved a remarkable H-2 evolution rate of 641.9 mu L h(-1) cm(-2) under AM 1.5 illumination, five times higher than that of the pure TiO2 photoanode.

Automated summary

The local photothermal effects of a CQDs/Au/TiO2 nanorod array composite photoanode were studied and modeled by an equivalent simplified temperature field model. The results showed that the local thermal effect stimulated the activity of TiO2, enhanced charge transfer and surface dynamic reaction. The combined effects of plasmonic Au nanoparticles and carbon quantum dots improved the carrier concentration and promoted bulk charge separation.