Fig. 5: Charge transfer pathways in QD-sensitized bulk photocatalysts.

a Electronic band diagram illustrating QD sensitization. QDs absorb light that is not efficiently utilized by the bulk photocatalyst, injecting carriers into its electronic bands based on their energy level alignment. This process leaves holes in the photoanode’s valence band or electrons in the photocathode’s conduction band. b PbS-QDs-sensitized TiO₂ nanotube photoanode under UV–Vis illumination. PbS harvests a broader range of energy than pure TiO₂, facilitating electron transfer through the lattice and extracting them under applied bias. Adapted from ref. ⁷⁵. Copyright 2022, Elsevier. c Rainbow-like CdSe-QD-sensitized NiO photocathode for PEC hydrogen evolution. Smaller CdSe-QDs (blue) have larger band gaps, while larger CdSe-QDs (red) display smaller band gaps due to the quantum confinement effect. Adapted from ref. ⁸².