Enhanced photoelectrochemical water splitting with WO₃/TiO₂ core/shell heterojunction photoanodes: Unveiling the role of dendritic TiO₂

This research presents a new approach for fabricating efficient photoanodes for water splitting by creating a core/shell heterojunction. The heterojunction consisted of vertically aligned WO₃ nanoplates as the core, with a dendritic TiO₂ nanoneedles array as a shell deposited onto fluorine-doped tin oxide (FTO) substrates. The WO₃ nanoplates are prepared through a hydrothermal method, and the TiO₂ shell is deposited using a cost-effective chemical bath deposition method. This unique architecture enhanced light absorption, promoting efficient charge separation and transport, which led to improved photoelectrochemical (PEC) performance for water splitting. The WO₃/TiO₂ heterojunction achieved a photocurrent density of 1.2 mA cm⁻² at 1.6 V vs. RHE and demonstrated 92 % PEC stability after 3 h under simulated solar illumination (1.5 G). The enhanced performance is attributed to the favorable band alignment, which enabled efficient charge transfer between the conduction bands of TiO₂ and WO₃, the improved light harvesting by the WO₃ nanoplates, and the excellent PEC stability of the TiO₂ shell.