Sol-Gel Synthesis and Characterization of Mesoporous TiO2 Modified with Transition Metal Ions (Co, Ni, Mn, Cu)

Self Cite

Produced by templated sol-gel method mesoporous nanosized titania powders modified with 3d-metal ions have been characterized by XPS and TPR methods. Metal species formed on the titania surface were investigated. The TPR analysis showed that reduction behaviors of the M n+ /TiO 2 were strongly affected by the synthesis method, preparation conditions and interactions between the dopant metal and TiO 2 matrix. It was found that Ti-O-M-bonds formation during sol-gel synthesis with applying nonionic triblock copolymer Pluronic P123 as organic template and calcination at 550 °C promoted high-dispersion states of doped 5 % metals. The XPS and TPR showing dopants exist as divalent and trivalent ions for M n+ /TiO 2 , where M=Co, Ni, Mn, and as monovalent and divalent ions in the case of Cu/TiO 2 .

Section: Resultssupporting

confidence: 84%

Section: Introductionmentioning

confidence: 99%

XPS and TPR study of sol-gel derived M/TiO2 powders (M=Co, Cu, Mn, Ni)

Petrik¹,

Krylova

Kelyp³

et al. 2015

Self Cite

“…Diffuse reflectance spectra (DRS) of the powders were recorded in spectral diapason 200-1000 nm using a Perkin-Elmer Lambda Bio 35 UV-Vis with an integrating sphere Labsphere RSA-PR-20 with BaSO 4 as a scattering standard and converted into ultraviolet-visible (UV-Vis) absorption spectra by the Kubelka-Munk function [26].…”

Section: Methodsmentioning

confidence: 99%

Synthesis O-g-C3N4/TiO2 rutile composite material for photocatalytic application

Bondarenko¹,

Silenko²,

Solonin³

et al. 2019

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 graphitelike 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.

Influence of the phase composition of the TiO2 matrix on the optical properties and morphology of deposited C3N4Ox nanoparticles

Bondarenko¹,

Silenko²,

Solonin³

et al. 2020

The use of oxygen modified graphite-like carbon nitride (C3N4Ox), photosensitive in the visible region of the optical spectrum, along with TiO2, photocatalytically active only in the ultraviolet region of the spectrum, in the C3N4Ox/TiO2 binary photocatalyst, opens a possibility of the use of sunlight energy. To increase opportunities of various kinds of photochemistry-related applications of C3N4Ox/TiO2 photocatalyst, the phase composition of the TiO2 matrix and morphology of nanoparticles of composite and their optical properties are very important. A novel composite material, C3N4Ox/TiO2, was synthesized in the present work in accordance with the approach developed in Frantsevich Institute for Problems of Materials Science of NASU for the synthesis of powdered oxygen-doped carbon nitride (C3N4Ox) by CVD method under the special reactionary conditions of the melamine pyrolysis, in particular, in the presence of a fixed air volume. Deposition of C3N4Ox carried out on the surface of a nanostructured powdered TiO2 matrix of different phase composition, rutile or anatase. The deposition of C3N4Ox (~5 % O) on both rutile and anatase nanopowders was confirmed by X-ray powder diffraction (XRD), scanning electron microscopy (SEM) with energy-dispersive X-ray spectroscopy (EDX), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and ultraviolet-visible diffuse reflectance spectroscopy (UV-Vis-DRS) methods. SEM micrographs (recorded with a MIRA3 TESCAN scanning electron microscope) of nanoparticles of both C3N4Ox/TiO2 composites (anatase and rutile phases) demonstrate the arrangement of TiO2 as separate globular nanoparticles and clusters between the plates and in the channels of the porous scaly plates C3N4Ox. However, the anatase phase nanoparticles (synthesized in IPM NASU) have a higher dispersion, the average size of non-aggregated almost monodisperse particles is about 10 nm. Using UV/Vis spectroscopy, it has been found that a redshift of long-wavelength edge of the fundamental absorption band of the spectra is observed when going from TiO2 (anatase), TiO2 (rutile), C3N4, C3N4Ox/TiO2 (anatase), C3N4Ox/TiO2 (rutile) and, then, to C3N4Ox, and the band gap decreases from 3.2, 3.0, 2.6, 2.4, 2.25 to 2.1 eV in the above sequence of materials. In such a case, C3N4Ox/TiO2 (especially deposited on anatase phase) would absorb more visible light than g-C3N4 and TiO2, by generating more charges which favor the improvement in the photoactivity of the catalysts.