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Highlights: [•] The photocatalytic mechanism of visible-light response N S codoped anatase TiO2 was first investigated by the first-principles. [•] The O-poor growth condition is beneficial to the formation of N S codoped anatase TiO2. [•] The bent and flat impurity levels were the separation and combination centers of photogenerated electrons and holes, respectively. [•] The dominant oxidant species during photocatalytic reaction for N S codoped TiO2 was hole and OH radical instead of O2 − ion. [ABSTRACT FROM AUTHOR]

Highlights: [•] Ag/TiO2 visible light photocatalyst was successfully fabricated using dielectric barrier discharge at atmospheric pressure. [•] XPS and XRD spectra proved that Ag ions were completely reduced to metallic Ag nanoparticles. [•] The Ag/TiO2 catalyst fabricated by DBD cold plasma exhibited a high activity for MB degradation under visible light (λ >420nm). [•] Atmospheric-pressure DBD cold plasma was highly efficient for preparation of supported metallic Ag catalyst. [Copyright &y& Elsevier]

Abstract: Mesoporous N,W co-doped TiO2 photocatalysts that contained various percentages of atomic tungsten dopant levels were synthesized by a facile solution combustion method which utilized urea as a nitrogen source and sodium tungstate as a tungsten source. The prepared samples were characterized by X-ray diffraction (XRD), transmission electron microscope (TEM), N2 physisorption, UV–vis absorbance spectroscopy, and X-ray photoelectron spectroscopy (XPS). The results reveal that the synthesized N and W co-doped TiO2 nanomaterials have high surface areas and mesoporous structures. In addition, the co-doping significantly narrows the band gap (∼2.7eV) that is responsible for the high visible light response of these samples in comparison to that of pure anatase TiO2 (∼3.2eV). The photocatalytic activity of the prepared samples was evaluated on the basis of the photodegradation rate of Rhodamine B under visible light (λ >420). It was found that the mesoporous N,W co-doped TiO2 nanomaterials fabricated in this study exhibited high visible light activity. This significant improvement in photocatalytic activity may be attributed to the synergistic effect of the red shift in absorption combined with a high surface area. [Copyright &y& Elsevier]

A visible-light photocatalyst was prepared by calcination of the hydrolysis product of Ti(SO_4)_2 with ammonia as precipitator. The color of this photocatalyst was vivid yellow. It could absorb light under 550 nm wavelength. The crystal structure of anatase was characterized by XRD. The structure analysis result of X-ray fluorescence (XRF) shows that doped-nitrogen was presented in the sample. The photocatalytic activities were evaluated using methyl orange and phenol as model pollutants. The photocatalytic activities of samples were increasing gradually with calcination temperature from 400°C to 700°C under UV irradiation. It can be seen that the degradation of methyl orange follows zero-order kinetics. However, the calcination temperatures have no significant influence on the degradation of phenol under sunlight. The N-doped catalyst shows higher activity than the bare one under solar irradiation. [ABSTRACT FROM AUTHOR]

We report a novel surfactant–TiO2 photochemical system where TiO2 in surfactant solutions exhibits visible light activities for the first time. In the presence of a simple nonionic surfactant having polyoxyethylene groups (Brij), CCl4 and Cr(VI) can be successfully converted in aqueous TiO2 suspensions under visible light illumination. A visible light induced electron transfer on surfactant–TiO2 reductively degrades CCl4 into Cl- and CO2 or reduces Cr(VI) to Cr(III). As a spectroscopic evidence for this visible light activity, a broad absorption band (320–500 nm) is observed in the surfactant–TiO2 solution. It is proposed as a hypothesis that a complex formation between the surfactant functional groups and TiO2 surface is responsible for the weak visible light absorption and the subsequent photoinduced electron transfer to CCl4 or Cr(VI). The visible light induced reduction of both CCl4 and Cr(VI) on TiO2 is strongly dependent on the kind of surfactants and only Brij-series show significant activities. The light absorption and the corresponding photoactivity are well correlated: the greater the absorption band, the higher the reactivity. Platinizing TiO2 particles rapidly decreases both the visible absorption and the visible reactivity since the Pt deposits mask the surface functional groups and consequently inhibit the complexation with the surfactant functional groups. Both the CCl4 dechlorination rate and the visible absorption band increase with the surfactant concentration, which indicates that more surface complexes are formed at higher surfactant concentrations. Although the visible light activity of this surfactant–TiO2 system has been demonstrated for the reduction of CCl4 and Cr(VI) only in this study, other photocatalytic or photoelectrochemical conversion processes that are based on the visible light-induced electron transfer on TiO2 surface might be also carried out using this system as a general method of TiO2 activation. [Copyright &y& Elsevier]

• N-doped TiO2 photocatalysts with tunable oxygen vacancies were prepared. • Photoinduced charge separation rate has been promoted. • The formation of O 2 − has been significantly improved. • The visible light photocatalytic activity has been enhanced. In this work, N-doped TiO 2 (N-TiO 2) with ample and tunable OVs was successfully synthesized, deriving from facile hydrothermal method and baked in the NH 3 atmosphere. N-doping boosts the amount of surface hydroxyl and superoxide (O 2 −) of TiO 2 , demonstrated by XPS and nitroblue tetrazolium (NBT)-O 2 − quantitative reaction. Rich and tunable OVs were confirmed by low temperature electron spin resonance (ESR) results, demonstrating that doping of N into TiO 2 can definitely construct higher OVs than the reference TiO 2. Surface photovoltage spectrum (SPS) test, fluorescence experiments and electrochemical measurements all display that N-TiO 2 photocatalysts with OVs have a higher severance efficiency of photogenerated e-/h+ pairs than the pristine TiO 2. Photocatalytic evaluation results exhibit that N-TiO 2 photocatalysts demonstrate better performance than the reference TiO 2 toward decontamination of rhodamine B and tetracycline. TiO 2 treated in ammonia atmosphere for 1 h shows the highest photocatalytic property. The visible light responsive catalytic behavior of TiO 2 treated in ammonia atmosphere for 1 h is much higher than that of commercial TiO 2 (P25) and the pristine TiO 2 , separately. The ameliorated visible light behavior of N-TiO 2 photocatalysts is attributable to rich oxygen vacancies produced through introducing N into TiO 2 and the boosted severance of photoactivated e-/h+. [ABSTRACT FROM AUTHOR]

In order to expand the use of titania indoor as well as to increase its overall performance, narrowing the band gap is one of the possibilities to achieve this. Modifying with rare earths (REs) has been relatively unexplored, especially the modification of rutile with rare earth cations. The aim of this study was to find the influence of the modification of TiO2 with rare earths on its structural, optical, morphological, and photocatalytic properties. Titania was synthesized using TiOSO4 as the source of titanium via hydrothermal synthesis procedure at low temperature (200 °C) and modified with selected rare earth elements, namely, Ce, La, and Gd. Structural properties of samples were determined by X-ray powder diffraction (XRD), and the phase ratio was calculated using the Rietveld method. Optical properties were analyzed by ultraviolet and visible light (UV-Vis) spectroscopy. Field emission scanning electron microscope (FE-SEM) was used to determine the morphological properties of samples and to estimate the size of primary crystals. X-ray photoelectron spectroscopy (XPS) was used to determine the chemical bonding properties of samples. Photocatalytic activity of the prepared photocatalysts as well as the titania available on the market (P25) was measured in three different setups, assessing volatile organic compound (VOC) degradation, NOx abatement, and water purification. It was found out that modification with rare earth elements slows down the transformation of anatase and brookite to rutile. Whereas the unmodified sample was composed of only rutile, La- and Gd-modified samples contained anatase and rutile, and Ce-modified samples consisted of anatase, brookite, and rutile. Modification with rare earth metals has turned out to be detrimental to photocatalytic activity. In all cases, pure TiO2 outperformed the modified samples. Cerium-modified TiO2 was the least active sample, despite having a light absorption tail up to 585 nm wavelength. La- and Gd-modified samples did not show a significant shift in light absorption when compared to the pure TiO2 sample. The reason for the lower activity of modified samples was attributed to a greater Ti3+/Ti4+ ratio and a large amount of hydroxyl oxygen found in pure TiO2. All the modified samples had a smaller Ti3+/Ti4+ ratio and less hydroxyl oxygen. [ABSTRACT FROM AUTHOR]