Abstract
In this study, we developed a glycerol-mediated safe and facile method to synthesize colored titania nanoparticles (NPs) via solution route. Our method is considerably effective and greener than other options currently available. Colored titania NPs were produced by hydrolyzing TiCl4 precursor in aqueous solution containing different concentrations of glycerol (0.0, 1.163, 3.834, and 5.815 mol/L) and subsequent calcination at 300 °C for 1 h. Our results highlight firstly that glycerol-mediated synthesis is unlikely to affect the anatase crystalline structure of TiO2, and secondly, that it would lead to coloration, band gap narrowing, and a remarkable bathochromic redshift of the optical response of titania. More importantly, the synthesized colored titania have Ti3+ ions, which, at least in terms of our samples, is the major factor responsible for its coloration. These Ti3+ species could induce mid gap states in the band gap, which significantly improve the visible light absorption capability and photocatalytic performance of the colored titania. The photocatalytic experiments showed that the colored TiO2 NPs prepared in 1.163 mol/L aqueous glycerol solution displayed the best photocatalytic performance. Almost 48.17% of phenolic compounds and 62.18% of color were removed from treated palm oil mill effluent (POME) within 180 min of visible light irradiation.
Highlights
TiO2 is a semiconductor metal oxide that is used in a variety of applications, including, but not limited to, photocatalytic hydrogen generation [1], organic synthesis of chemicals [2], dye-sensitized solar cells [3], and environmental remediation [4,5,6]
It has become a common research hotspot to shift the optical response of TiO2 into the visible light range and narrow its band gap in order to improve its overall efficiency for solar-driven visible light photocatalysis
The results reveal that the synthesized colored TiO2 NPs improved visible and infrared light absorption, narrow bandgap, and Ti3+ ions
Summary
TiO2 is a semiconductor metal oxide that is used in a variety of applications, including, but not limited to, photocatalytic hydrogen generation [1], organic synthesis of chemicals [2], dye-sensitized solar cells [3], and environmental remediation [4,5,6]. When TiO2 is used as a photocatalyst, it produces excited charges (electron and hole) upon irradiation by light energy higher than its bandgap. These charge carriers transfer to the TiO2 surface to carry out the photocatalytic reaction, before their recombination [7]. The more light absorbed by TiO2, the more likely the working electron and hole are present on the surface to perform photocatalytic reactions [8]. Because of the wide bandgap of TiO2 (3.0–3.2 eV), it is unable to efficiently absorb visible light, which makes up 45% of the solar radiations [1,9]. It has become a common research hotspot to shift the optical response of TiO2 into the visible light range and narrow its band gap in order to improve its overall efficiency for solar-driven visible light photocatalysis
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