(0 0 1) Facets optimized surface oxygen vacancies in TiO2 films to enhance photocatalytic antibacterial and hydrophilic properties

Abstract

Oxygen vacancies (OVs) engineering is one of the most common methods for enhancing the photocatalytic activities of titanium dioxide (TiO2). Although the effect is affected by the spatial distribution of OVs, little is known about how exposed facets affect the generated OVs. Therefore, we fabricate the anatase-TiO2 films with different preferred orientations ((001) and (101) facets) on glass by magnetron sputtering and heat treatment, after that the OVs are induced in TiO2 films by hydrogen plasma treatment at 300 °C. Through ultraviolet–visible spectroscopy, X-ray photoelectron spectroscopy and electron paramagnetic resonance analyses, the results indicate that (001) preferred orientation raise the concentration of surface OVs due to the lower OVs formation energy and the higher barrier for subsurface migration. The (001) preferred film (ht-p_2) shows the best photocatalytic performance. Within 150 min of being exposed to UV light, the degradation rate constants of methyl orange (MO) can reach 0.0029/min and 0.0022/min in 12 mg/L and 24 mg/L, respectively, which are about 2.4 times higher than the film without (001) preference. Transient photocurrent test results of ht-p_2 with the obvious increase in current density (24.9 μA/cm2) also prove that the TiO2 film with more surface OVs has a higher carrier separation efficiency, which plays a significance role in promoting the photocatalytic activities. What’s more, the results of photoinduced hydrophilicity and photocatalytic antibacterial are consistent with the photocatalytic degradation performance. This work confirms that the preferred orientation facets of TiO2 films can be used to improve the hydrophilic antibacterial properties via controlling surface OVs, which benefit the design of high-performance catalyst.