Abstract
In this study, the photocatalytic properties of novel keratin char-TiO2 composite films, made through the calcination of wool keratin coatings containing TiO2 precursors at 400 °C, were investigated for the photodegradation of organic contaminants under visible light irradiation. Its structural characteristics and photocatalytic performance were systematically examined. It was shown that a self-cleaning hydrophobic keratin char-TiO2 composite film containing meso- and micro-pores was formed after the keratin—TiO2 precursors coating was calcined. In comparison with calcinated TiO2 films, the keratin char-TiO2 composite films doped with the elements of C, N, and S from keratins resulted in decreased crystallinity and a larger water contact angle. The bandgap of the char-TiO2 composite films increased slightly from 3.26 to 3.32 eV, and its separation of photogenerated charge carriers was inhibited to a certain degree. However, it exhibited higher photodegradation efficiency to methyl blue (MB) effluents than the pure calcinated TiO2 films. This was mainly because of its special porous structure, large water contact angle, and high adsorption energy towards organic pollutants, confirmed by the density functional theory calculations. The main active species were 1O2 radicals in the MB photodegradation process.
Highlights
The semiconductor TiO2 can be used in a wide range of applications such as paints, cosmetics, photoelectric sensors, energy conversion and storage, air and water purifications, and removal of organic pollutants [1]
The electrochemical impedance spectroscopy (EIS) Nyquist plots indicated that both the semicircle arcs of the calcined films were very close in the high-frequency region, implying there was no significant difference in the charge-transfer resistance for the calcined TiO2 film and calcined keratin char-TiO2 composite film [54]
The hydrophobic self-cleaning keratin char-TiO2 composite films were made from the calcination of keratin-TiO2 films for the photocatalytic degradation of dye pollutants
Summary
The semiconductor TiO2 can be used in a wide range of applications such as paints, cosmetics, photoelectric sensors, energy conversion and storage, air and water purifications, and removal of organic pollutants [1]. Doping TiO2 with metal or non-metal elements is regarded as an effective and feasible strategy for enhancing light harvesting and minimizing the energy band gap of TiO2 [10]. It broadens the photo-response range towards visible light or infrared, thereby inhibiting the recombination of photogenerated electron-hole pairs [11]. TiO2 film is endowed with unique mechanical, physical, and chemical features, including tunable band gap, high refractive index, large surface area, and enhanced photocatalytic activity [19]. It is envisaged that keratin char-TiO2 nanoparticle composite catalysts could still be doped owf i2t4h the elements of C, N, S from keratin and might still have higher efficiency while resistant to harsh alkaline effluents conditions. It was noticed that a compact coating was homogeneously deposited on the glass substrate for all four
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