Abstract
The development of novel materials ensuring the use of solar radiation as an inexhaustible source of renewable and environmentally friendly energy is one of the actual problems of materials science. Scientific research towards of solving this important task showed the expediency of using photocatalytic processes with the participation of semiconductor systems. One of the most well-known catalyst titanium dioxide TiO 2 has photoactivity only in the ultraviolet region of the spectrum that significantly restricts its use. The application of based on undoped graphite-like carbon nitride g-C 3 N 4 or g-C 3 N 4 /TiO 2 composite catalysts allows using only part of the visible spectrum of solar radiation (with a wavelength of less than 460 nm). It is found that the doping of carbon nitride by oxygen significantly improves its photocatalytic properties to enhancing solar energy utilization. Therefore, to improve the photocatalytic activity of semiconductor photocatalyst, the coupling O-doped g-C 3 N 4 (O-g-C 3 N 4 ) with rutile TiO 2 is a good strategy. Novel composite material O-g-C 3 N 4 /TiO 2 was synthesized by gas phase method of deposition of O-doped g-C 3 N 4 on particles of rutile powder under the special reactionary conditions of the pyrolysis of melamine. Obtaining O-g-C 3 N 4 /TiO 2 binary composite was confirmed through various analytical techniques including X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and ultraviolet-visible diffuse reflectance spectra (UV-Vis-DRS) methods. It is found that the absorption spectra of the O-g-C 3 N 4 /TiO 2 powders show a bathochromic shift of the long-wavelength edge of the fundamental absorption band (to 600 nm) relative to the absorption band of g-C 3 N 4 /TiO 2 (~ 460 nm). As a result, O-g-C 3 N 4 /TiO 2 photosensitivity is observed in the significant part of the visible region and the band gap of synthesized product is determined to be less than 2.4 eV versus 2.7 eV for undoped g-C 3 N 4 or g-C 3 N 4 /TiO 2 . One stage constructing heterojunction structure of O-g-C 3 N 4 /TiO 2 composite may be used as a low-cost way to avoid the limitations of each component and realize a synergic effect in promoting the efficient generation and separation of charge carriers, thus boosting the photocatalytic activity to enhancing solar energy utilization.
Highlights
Using sunlight by semiconductors for the production of renewable and clean energy and purification of water and air from toxic organic pollutants and pathogenic microflora is considered as a promising approach to address the imperative energy and environment problems [1,2,3,4,5]
Its photocatalytic activity is limited by rapid photogenerated electron-hole recombination and, most importantly, its wide band gap energy of ca. 3 eV (~ 3.2 and ~ 3.0 eV for anatase and rutile, respectively) which is activated only under ultraviolet (UV) light irradiation that accounts for about 5 % of solar light
New composite material – O-g-C3N4/TiO2 was synthesized in accordance with the one-step method developed in in the experiments the synthesized (IPM) for the synthesis of oxygen-doped carbon nitride (O-g-C3N4) by gas phase method under the special reactionary conditions of the pyrolysis [25] of melamine [18], urea [19,20,21] or cyanuric acid and urea mixture [22]
Summary
New composite material – O-g-C3N4/TiO2 (rutile phase) was synthesized in accordance with the one-step method developed in IPM for the synthesis of oxygen-doped carbon nitride (O-g-C3N4) by gas phase method under the special reactionary conditions of the pyrolysis [25] of melamine [18], urea [19,20,21] or cyanuric acid and urea mixture [22]. To confirm the accordance of the obtained light yellow powder with the O-g-C3N4/TiO2 composition, in the experiments the synthesized (IPM) O-doped carbon nitride (O-g-C3N4) [18], pristine g-C3N4 and TiO2 (rutile phase) powdered samples used.
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