Kronos Vlp7000 Research Articles

Production of hydrogen by water photo-splitting over commercial and synthesised Au/TiO2 catalysts

H2 production from methanol/water photo-splitting was compared using various commercial photocatalysts (Evonik P25 (P25), Hombikat UV-100 (HB) and Kronos vlp7000 (KR)) and others synthesised with a sol–gel-hydrothermal (HT) process and a sol–gel method followed by calcination (SG400 and SG750). All photocatalysts had been surface modified with Au at different concentrations, from 0.2 to 6.0wt.%, using the photodeposition method. A complete characterisation study of the different photocatalysts was performed (BET, XRD, TEM, SEM-EDX, FTIR, UV–vis Reflectance Diffuse Spectra and aggregate size). The experiments were conducted for 3.5h using 1gL−1 of photocatalyst with methanol (25vol.%) as sacrificial agent. In addition to H2 generation, production of the main intermediates, formaldehyde and formic acid, and of CO2 was also evaluated. The commercial photocatalyst KR at 0.8wt.% Au had the highest H2 production of all the photocatalysts studied with 1542.9μmolh−1. Of the photocatalysts synthesised by our group, SG750 at Au loading of 2.0wt.% gave the highest H2 production of 723.1μmolh−1. The SG750 photocatalyst at Au loading of 2.0wt.% also had the highest H2 production yield per unit of surface area at 45.5μmolgh−1m−2.

Hydrogen production using Pt-loaded TiO2 photocatalysts

A series of synthesised TiO2-based and commercial photocatalysts were modified by Pt photodeposition and a study made of their photocatalytic activity in hydrogen production. The modified commercial photocatalysts were Evonik P25, Kronos vlp7000 and Hombikat UV-100, and the other modified photocatalysts were synthesised by our group using sol–gel and sol–gel hydrothermal processes (SG400, SG750 and HT). Pt weight percentages used in the study were 0.5, 1.0 and 2.1 wt.% (Pt/TiO2). The photocatalysts were extensively characterised by X-ray diffraction (XRD), UV–vis diffuse reflectance, Brunauer–Emmett–Teller (BET) surface area measurement, transmission electron microscopy (TEM), scanning electron microscopy (SEM–EDX), Fourier transform infrared spectroscopy (FTIR) and laser light dispersion. Methanol (25% vol.) was used as sacrificial agent over the 8 h of the hydrogen production tests and measurements were taken of the final concentrations of formaldehyde and formic acid as well as initial and final TOC. Photoactivity of all photocatalysts increased in the presence of Pt. The most efficient of the synthesised photocatalysts was SG750 and of the commercial photocatalysts P25. Maximum production of SG750 was 1846 μmol h−1 at 1.0 wt.% Pt and its production per surface unit was notably higher than that of P25.

Evaluation of UV and visible light activity of TiO2 catalysts for water remediation

The photocatalytic activity under UV, visible and UV–visible radiation of two commercial catalysts for water remediation are evaluated and compared in a slurry reactor. Bisphenol A (BPA) was employed as the model pollutant. The activities of the carbon-doped, TiO2 catalyst Kronos vlp 7000 and, as a reference, the undoped catalyst Aeroxide P25 are compared by means of efficiency parameters: the overall photonic efficiency and the quantum efficiency. For the evaluation of the radiation absorbed by the catalyst suspensions, the optical properties of TiO2 Kronos vlp 7000 between 300 and 550nm were measured and reported, as well as the properties of TiO2 Aeroxide P25 in the range 400–550nm. Kronos catalyst exhibits absorption in the visible range and was almost three times more efficient than Aeroxide for BPA degradation under this condition. However, under UV radiation, Aeroxide P25 quantum efficiency was about 1.5 times the corresponding value of Kronos. Similar BPA photonic and quantum efficiencies were obtained under UV–visible radiation with both commercial catalysts.

Efficient and affordable hydrogen production by water photo-splitting using TiO2-based photocatalysts

TiO2-based photocatalyst materials were synthesized through a sol–gel method, followed either by: (1) hydrothermal treatment (150 °C/24 h), or (2) heat treatment (calcination) in a temperature range between 400 and 900 °C. The resulting materials were characterized through BET, XRD, TEM, FTIR, RAMAN, laser diffraction and UV–Vis Diffuse Reflectance Spectroscopy. Photoactivity of the various materials was checked against photocatalytic water-splitting for hydrogen production and a relationship between TiO2 structure and hydrogen production capacity was identified. Optimum results were obtained for anatase-rutile mixtures in a ratio of 87:13. The activity of the home-made photocatalysts was also compared (under the same conditions) with the best commercially available materials which have been widely described in the literature: Hombikat UV100, Millenium PC100, Kronos vlp7000,Degussa P25and Kemira 625.

Comparison of the photocatalytic efficiencies of bare and doped rutile and anatase TiO2 photocatalysts under visible light for phenol degradation and E. coli inactivation

This study aimed at comparing the photocatalytic efficiencies of various TiO2 based photocatalysts for phenol degradation and bacteria inactivation under illumination with visible light. Commercial undoped anatase and rutile (both from Aldrich), Aeroxide P25 (Evonik Industries), nitrogen-doped anatase (Sumitomo TP-S201, Sumitomo Chemical Inc.), nitrogen and sulphur co-doped anatase (Kronos VLP7000, Kronos Titan GmbH), and our custom-synthesized nitrogen- and iron-doped TiO2, as well as nitrogen and sulphur co-doped Aeroxide P25 and silver- and gold-deposited Aeroxide P25 were studied. The photocatalytic efficiency of different types of titanium dioxide based photocatalysts was determined by inactivation of Escherichia coli K12 bacteria and by phenol decomposition. Electron spin resonance (ESR) in combination with spin trapping was used to get insight into the reactive oxygen species (ROS)-mediated photocatalytic processes in the presence of TiO2-based photocatalysts. ESR results confirmed that titanias which generated OH radicals were efficient in E. coli disinfection, whereas titanias that were unable to produce OH radicals did not reveal significant bactericidal action. Three of our home-made titanias (iron-, nitrogen-, nitrogen/sulphur) as well as the commercial nitrogen/sulphur codoped Kronos VLP7000 TiO2 showed higher efficiency of phenol degradation than the well-established reference photocatalyst, Aeroxide P25, but showed much lower (if any) activity for bacteria inactivation, including Kronos VLP7000, which revealed extremely high efficiency for phenol decomposition. Interestingly undoped Aldrich rutile (with large particles - 100–700nm) had the highest efficiency for inactivation of E. coli and also had fairly high activity of phenol degradation.

Deactivation and regeneration of visible light active brookite titania in photocatalytic degradation of organic dye

This study was performed to investigate deactivation and regeneration of predominantly brookite titania powders. Visible light active (VLA) polymorphic titania particles were prepared by a water-based ambient condition sol (WACS) process followed by a solvent-based ambient condition sol (SACS) process with N-methylpyrrolidone (NMP) as the solvent. Deactivation of all samples was evaluated by degradation of methyl orange (MO) dye under either UV or VL irradiation for four reaction cycle runs. The photocatalytic activity (PCA) under VL exposure of NMP samples calcined at 200 °C for 2 h in air (NMP-200) was approximately 3.3 times higher than that of a commercial VLA titania (Kronos VLP7000), despite the much lower surface area of the NMP-200. Nonetheless, PCA of all titania samples under VL gradually decreased with an increase in testing time and number of runs. The cause of the deactivation of the titania samples in this study was identified as the deposition of the decomposed MO on the titania nanoparticle surface. Among the possible regeneration or reactivation procedures for the used samples, methanol washing was shown to be the most effective up to ∼80% of the PCA recovery. The used NMP-200 samples could not completely be recovered, since a regeneration process would possibly remove some of nitrogen species responsible for the VLA.

Nature of the Oxidizing Species Formed upon UV Photolysis of C-TiO2 Aqueous Suspensions

UV photolysis of aerated aqueous suspensions of C-TiO2 (KRONOS vlp 7000) or TiO2 (KRONOS uvlp 7500, Degussa P25) containing CH3OH produces HCHO and H2O2, and the latter accumulates only in the case of C-TiO2. The UV photolysis of C-TiO2 in aerated suspensions produces holes, which oxidize CH3OH to •CH2OH leading to the formation of HCHO in the presence of oxygen. H2O2 produced via the oxidation of CH3OH to HCHO and through the reduction of O2 by the conduction band or trapped electrons is adsorbed by all titania. Catalase, which catalyzes CH3OH oxidation by H2O2, substantially increases the rate of HCHO formation only in the case of C-TiO2. This observation indicates that the electrons produced upon UV excitation of C-TiO2 differ from those of unmodified TiO2 with respect to their reactivity toward the photolytically generated H2O2. The holes produced in P25 behave differently from those formed in C-TiO2 and uvlp 7000 with respect to their reaction with added H2O2. This difference is, at least in part, du...