Physiochemical properties of n-n heterostructured TiO₂/Mo-TiO₂ composites and their photocatalytic degradation of gaseous toluene

Abstract

The composite TiO 2 /Mo-TiO 2 were prepared by a modified sol-gel method. The prepared catalysts were characterized by X-ray diffraction, BET analysis, SEM, X-ray photoelectron spectroscopy, and UV-vis diffused reflectance spectroscopy techniques. The structural characterization results demonstrated that Mo was successfully doped into the TiO 2 lattice and caused slight changes in the physiochemical properties. The UV-vis DRS showed a red shift of the adsorption edge to the visible region. The photocatalytic decomposition efficiencies of the catalysts were examined with toluene as a typical VOC in a continuous flow reactor. The photocatalytic activity of the n-n heterogeneous TiO 2 /Mo-TiO 2 was greater than that of pure TiO 2 and Mo-TiO 2 , and the catalyst containing a Mo/Ti mole ratio of 2.5% exhibited optimum photocatalytic properties. In general, a relative humidity of 35%, a higher oxygen content, a lower initial toluene concentration, and a higher UV intensity were beneficial for toluene decomposition.

Enhanced Photoelectrochemical Properties from Mo-Doped TiO2 Nanotube Arrays Film

“…Theoretically, by offering more valence electrons easily photo-incited and converting to free carriers, Mo doping with low concentration introduces a donor level below the conduction band of TiO2, resulting in a narrower band gap [7]. The shifted band gap can be evaluated from the absorption spectrum by the Tauc method [26,30]. The estimated band gap of undoped TiO2 is 3.24 eV, agreeing with the typical value of intrinsic pure TiO2 [20].…”

“…In numerical terms, the ionic radius of Ti 4+ (0.068 nm) is very close to the ionic radius of Mo 6+ (0.062 nm), and when the amount of doping is not too high (0.5 at.%), most of Mo 6+ ions replace Ti 4+ as substitutional impurities. In the case of heavy doping (1.0 at.%), excess Mo enters the lattice only in the form of interstitial atoms, which aggravates the lattice deformation and suppresses grain growth [26]. Some researchers suggest that the doping of Mo inhibits growth of crystals due to induced structure defects and hinders the transformation from anatase to rutile of TiO 2 at the same time [7,27].…”

Recent progress in biochar-supported photocatalysts: synthesis, role of biochar, and applications

“…4 Therefore, an external UV light source is required for their activation, which is not a cost-effective method. However, various hybrid composites synthesized by combining doping of transition metals (Ti, Fe, Ru, Au, and Mo) [8][9][10][11] and/or non-metals (C, N, and S) [12][13][14] can improve the photocatalytic performance, but, high preparation costs, non-renewability, and risks of secondary pollution prevent their large-scale application. Therefore, more and more attention has been applied to giving a stable platform for photocatalytic nanoparticles by incorporating secondary materials, which can improve the recoverability and visible light sensitivity of the photocatalysts.…”

Preparation of TiO2 and Fe-TiO2 with an Impinging Stream-Rotating Packed Bed by the Precipitation Method for the Photodegradation of Gaseous Toluene

“…Moreover, the photocatalytic performance restricts its development and application: firstly, the band gap of 3.2 eV limits it to using only ultraviolet light below 387.5 nm in wavelength [8]. Secondly, the electron and hole produced by the light excitation of TiO 2 recombine very easily [9,10]. Therefore, developing preparation technology of TiO 2 with good dispersion and a uniform particle size and exploring a way to broaden the light response range and inhibit the electron and hole recombination of TiO 2 are the key problems which need to be solved urgently in order to develop the commercialization and advanced application of nano-TiO 2 .…”