Synergistic Effect of CdSe Quantum Dot Sensitization and Nitrogen Doping of TiO2 Nanostructures for Photoelectrochemical Solar Hydrogen Generation

Abstract

We report the synthesis and photoelectrochemical (PEC) studies of TiO₂ nanoparticles and nanowires simultaneously doped with nitrogen and sensitized with CdSe quantum dots (QDs). These novel nanocomposite structures have been applied successfully as photoanodes for PEC hydrogen generation using Na₂S and Na₂SO₃ as sacrificial reagents. We observe significant enhanced photoresponse in these nanocomposites compared to N-doped TiO₂ or CdSe QD sensitized TiO₂. The enhancement is attributed to the synergistic effect of CdSe sensitization and N-doping that facilitate hole transfer/transport from CdSe to TiO₂ through oxygen vacancy states (V_o) mediated by N-doping. The results demonstrate the importance of designing and manipulating the energy band alignment in composite nanomaterials for fundamentally improving charge separation and transport and thereby PEC properties.