Abstract
TiO2/TiOF2 nanohybrids were quickly synthesized through a hydrothermal process using titanium n-butoxide (TBOT), ethanol (C2H5OH) and hydrofluoric acid as precursors. The prepared nanohybrids underwent additional NaOH treatment (OH-TiO2/TiOF2) to enhance their photocatalytic performance. In this paper, the mechanism of NaOH affecting the pathway of transformation from TBOT (Ti precursor) to TiO2 nanosheets was discussed. The synthesized TiO2/TiOF2 and OH-TiO2/TiOF2 were characterized by field emission scanning electron microscopy (FE-SEM), high-resolution transmission electron microscopy (HRTEM), X-ray diffraction pattern (XRD), Fourier infrared spectroscopic analysis (FT-IR), Photoluminescence (PL) emission spectra and UV–visible diffuse reflection spectra (UV–vis DRS). The photocatalytic activity and stability of synthesized samples were evaluated by degradation of methylene blue (MB) under the simulated solar light. The results showed that a larger ratio of TiO2 to TiOF2 in TiO2/TiOF2 and OH-TiO2/TiOF2 nanohybrids could allow for even higher MB conversion compared with only TiO2 nanosheets. NaOH treatment can wash off the F ions from TiOF2 and induce this larger ratio. The highest efficiency of MB removal was just above 90% in 1 h. Lower electron–hole pairs recombination rate is the dominant factor that induces the photocatalytic performance enhancement of TiO2/TiOF2 nanohybrids. The synthesized OH-TiO2/TiOF2 nanohybrids exhibit great potential in the abatement of organic pollutants.
Highlights
As one of the most important materials, TiO2 has been widely used as a promising catalyst due to its lack of toxicity, high stability and easy preparation
Zhao et al [14] reported on a Pd@TiO2/TiOF2 photocatalyst made of TiO2 shell and TiOF2 core and further improved its performance by loading Pd nanoparticles onto the surfaces of TiO2/TiOF2 heterostructure, its synthesis process is complex
It can be seen that with a longer reaction time, the ratio of peak height of (100) for TiOF2 and TiO2 for (101) changed from 0.44 to 4.4–4.5 and to 0.55. This indicates that TiO2 existed at the beginning, before the level decreased and was dominated by other compounds, appeared and dominated again
Summary
As one of the most important materials, TiO2 has been widely used as a promising catalyst due to its lack of toxicity, high stability and easy preparation. Faults of a wide energy band gap (3.1–3.2 eV, meaning it only responds to UV light) and high electron– 2 hole recombination, which hinders its use under solar or visible light [1,2,3,4]. Wang et al [13] discovered a type of TiOF2 photocatalyst that possesses proper activity and strong durability in photocatalytic degradation of rhodamine B and 4-chlorophenol under visible light, its photocatalytic performance is not ideal. Zhao et al [14] reported on a Pd@TiO2/TiOF2 photocatalyst made of TiO2 shell and TiOF2 core (labelled as TiO2/TiOF2) and further improved its performance by loading Pd nanoparticles onto the surfaces of TiO2/TiOF2 heterostructure, its synthesis process is complex
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