Indium-Tin-Oxide Nanowire Array Based CdSe/CdS/TiO₂ One-Dimensional Heterojunction Photoelectrode for Enhanced Solar Hydrogen Production

For photoelectrochemical (PEC) hydrogen production, low charge transport efficiency of a photoelectrode is one of the key factors that largely limit PEC performance enhancement. Here, we report a tin-doped indium oxide (In₂O₃:Sn, ITO) nanowire array (NWs) based CdSe/CdS/TiO₂ multishelled heterojunction photoelectrode. This multishelled one-dimensional (1D) heterojunction photoelectrode shows superior charge transport efficiency due to the negligible carrier recombination in ITO NWs, leading to a greatly improved photocurrent density (∼16.2 mA/cm² at 1.0 V vs RHE). The ITO NWs with an average thickness of ∼12 μm are first grown on commercial ITO/glass substrate by a vapor-liquid-solid method. Subsequently, the TiO₂ and CdSe/CdS shell layers are deposited by an atomic layer deposition (ALD) and a chemical bath deposition method, respectively. The resultant CdSe/CdS/TiO₂/ITO NWs photoelectrode, compared to a planar structure with the same configuration, shows improved light absorption and much faster charge transport properties. More importantly, even though the CdSe/CdS/TiO₂/ITO NWs photoelectrode has lower CdSe/CdS loading (i.e., due to its lower surface area) than the mesoporous TiO₂ nanoparticle based photoelectrode, it shows 2.4 times higher saturation photocurrent density, which is attributed to the superior charge transport and better light absorption by the 1D ITO NWs.