Production of hydrogen by photoelectrochemical system has received considerable interest as one of the promising route without generation any undesired pollutants. A major component of a photoelectrochemical (PEC) water splitting system is the photoelectrode where critical processes such as light harvesting, generation of charge carriers, minority carrier migration towards its interface with the electrolyte, as well as majority carrier transportation towards the external circuit for water splitting. Co-sensitization by double-shell of QDs (e.g., CdSe/CdS) for the TiO₂ or ZnO nanostructures demonstrated a large PEC performance improvement due to their extension of light absorption range. A sequential coating of two different light absorbers on the electrode (e.g. CdS/CdSe multilayer structure on TiO₂) forms terraces in their band diagram (i.e, type II heterojunction), thus the aligned band edge promotes separation of electrons and holes and cascade-like carrier transport at their interface, and thereby increases the photocurrent The deposition of these QDs on one-dimensional (1-D) nanostructures of semiconductor including nanowires/nanorods (NWs/NRs) and nanotubes (NTs) increases the charge transport properties by providing a “highway” for electron travel. Although a few recent studies have shown that the ITO NWs improves the charge transport/collection for a single layer light absorber, their overall PEC performance is still lower than theoretically expected value because the photoelectrode absorb only a part of visible light (by a single layer absorber) and/or photo-generated charge carriers are largely recombined in the light absorber layer due to a low charge separation efficiency.

In the present study, we employed In₂O₃ and SnO₂ NWs as a support for the CdSe/CdS/TiO₂ multi-shelled heterojunction photoelectrode to demonstrate a largely enhanced PEC hydrogen production by improving the charge transport property. PEC performance of the resultant CdSe/CdS/TiO₂/ITO NWs photoelectrode for the hydrogen production was investigated and they are compared with those of a planar structured and m-TiO₂ nanoparticles based CdSe/CdS heterojunction photoelectrodes. The resultant 1-D heterojunction photoelectrode (CdSe/CdS/TiO₂/ITO NWs) shows improved light absorption and charge transport properties in comparison to the planar structured photoelectrode (without the ITO NWs) and mesoporous TiO₂ nanoparticles film based photoelectrode. We found that the ITO NWs based CdSe/CdS/TiO₂ multi-shelled photoelectrode exhibits photocurrent density of ~16.2 mA/cm², which is 2.4 times higher than that of m-TiO₂ nanoparticles based photoelectrode and even outperforms previously reported TiO₂ or ZnO NWs based photoelectrodes.