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

Abstract

As a well-known semiconductor that can catalyse the oxygen evolution reaction, TiO2 has been extensively investigated for its solar photoelectrochemical water properties. Unmodified TiO2 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 GaOxNy cocatalysts on TiO2 1D nanowires (TiO2@GaOxNy core-shell) using atomic layer deposition. We show that this modification significantly enhances the photoelectrochemical performance compared to pure TiO2 NW photoanodes. For our most active TiO2@GaOxNy core-shell nanowires with a GaOxNy 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 TiO2 NWs. Furthermore, the band gap matching with TiO2 enhances absorption of visible light over unmodified TiO2 and the facile oxygen vacancy formation after deposition of GaOxNy also provides active sites for water activation. Density functional theory studies of model systems of GaOxNy-modified TiO2 confirm the band gap reduction, high reducibility and ability to activate water. The highly efficient and stable systems of TiO2@GaOxNy core-shell nanowires with ALD deposited GaOxNy demonstrates a good strategy for fabrication of core-shell structures that enhances the photoelectrochemical performance of readily available photoanodes.