Amorphous TiO₂ coated hierarchical WO₃ Nanosheet/CdS Nanorod arrays for improved photoelectrochemical performance

This work demonstrates hierarchical WO₃ nanosheet/CdS nanorod (WO₃-NS/CdS-NR) arrays as a type-II heterojunction photoanode for improved photoelectrochemical (PEC) water splitting. Due to the synergistic effect of different constituents in the novel hierarchical structure, WO₃-NS/CdS-NR arrays as a photoanode yield a photocurrent density of 5.4 mA cm⁻² at 0.8 V versus reversible hydrogen electrode for sulfite oxidation. This is 12 times that of WO₃-NS arrays (0.45 mA cm⁻²) and 3 times that of CdS-NR arrays (1.85 mA cm⁻²). In this hybrid WO₃-NS/CdS-NR arrays photoanode, the favorable heterojunction between WO₃ and CdS enhances the charge separation efficiency and widens the light absorption spectrum. Furthermore, the optimization of the loading amount and size of CdS-NRs allows for a larger specific surface area as well as more effective light scattering, which further improves the PEC performance of WO₃-NS/CdS-NR arrays. Finally, the coating of an ultrathin layer of amorphous TiO₂ also enhances the photostability of WO₃-NS/CdS-NR arrays.