Modification of 1D TiO2 nanowires with GaOxNy by atomic layer deposition for TiO2@GaOxNy core-shell nanowires with enhanced photoelectrochemical performance

As a well-known semiconductor that can catalyse the oxygen evolution reaction, TiO ₂ has been extensively investigated for its solar photoelectrochemical water properties. Unmodified TiO ₂ shows some issues, particularly with respect to its photoelectrochemical performance. In this paper, we present a strategy for the controlled deposition of controlled amounts of GaO _xN _y cocatalysts on TiO ₂ 1D nanowires (TiO ₂@GaO _xN _y core-shell) using atomic layer deposition. We show that this modification significantly enhances the photoelectrochemical performance compared to pure TiO ₂ NW photoanodes. For our most active TiO ₂@GaO _xN _y core-shell nanowires with a GaO _xN _y thickness of 20 nm, a photocurrent density up to 1.10 mA cm ^-2 (at 1.23 V vs. RHE) under AM 1.5 G irradiation (100 mW cm ^-2) has been achieved, which is 14 times higher than that of unmodified TiO ₂ NWs. Furthermore, the band gap matching with TiO ₂ enhances the absorption of visible light over unmodified TiO ₂ and the facile oxygen vacancy formation after the deposition of GaO _xN _y also provides active sites for water activation. Density functional theory studies of model systems of GaO _xN _y-modified TiO ₂ confirm the band gap reduction, high reducibility and ability to activate water. The highly efficient and stable systems of TiO ₂@GaO _xN _y core-shell nanowires with ALD deposited GaO _xN _y demonstrate a good strategy for the fabrication of core-shell structures that enhance the photoelectrochemical performance of readily available photoanodes.