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

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-0) 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.