The development of efficient TiO2-based photocatalysts for water treatment is mainly performed by doping with transition metals or by establishing junctions between different phases, metal–semiconductor or semiconductor–semiconductor. We present, for the first time, the synthesis of Zr- and Mn-modified TiO2 by a redesigned sol–gel technique that allows the formation of heterometallic bridges on the TiO2 surface. Cations of the doping metals are located in the pores of mesoporous anatase and attached to the crystalline TiO2 walls. The presence of the Zr enhances the photoactivity of the TiO2 catalyst. However, the introduction of Mn decreases the photocatalytic efficiency in a nonadditive manner. The inhibition effect was assigned to the side reaction between hydroxyl radicals and Mn ions. The fact that Mn effectively scavenges the hydroxyl radicals and, consequently, inhibits the whole oxidation process is direct proof that hydroxyl radicals are the main reactive species in the photocatalytic oxidative processes on TiO2 surfaces in aqueous media and the process of OH radicals generation is the rate-determining step, which wasconfirmed using a method based on the decolorization of a commercial dye Bezaktiv Blau in a reaction with Fenton's reagent as a source of hydroxyl radicals.
COBISS.SI-ID: 5943322
The present research reports on a successful strategy of titanium dioxide modification with carbon and zirconium, for enhanced photocatalytic activity under UV–vis irradiation. Carbon and/or zirconium modified TiO2 nanoparticles were synthesized via sol–gel hydrothermal method. It was found that both elements positively influence important parameters for the photocatalytic activity improvement, such as crystallite size, diameter of agglomerates and surface area, summing their effects in case of codoped sample. Moreover, carbon modification shifts the absorption edge toward larger wavelength and decreases band gap energy in opposite to zirconium, which induces blue shift and increases the band gap energy. Thus, modification with two elements at a time narrows the band gap energy of co-doped sample maintaining its high oxidation potential, which along with increased absorption of visible light leads to enhancement in visible and ultraviolet light driven photocatalytic decomposition of methylene blue. It was found that Zr,Csingle bondTiO2 sample is more efficient photocatalyst for both visible and ultraviolet light driven processes than either of the pure or single element modified TiO2.
COBISS.SI-ID: 6071322
The rate of methylene blue and terephthalic acid degradation assisted with double metal-modified catalyst (0.1 mol% Cu and 1.0 mol% Zr) was enhanced as compared with single metal-modified catalysts (0.1, 0.5 mol% Cu and 1.0 mol% Zr). The wet impregnation method was used for copper and zirconium modification of the surface of Aeroxide P25 TiO2 particles. Simultaneous loading of both metals on the surface of P25 leads to an increased specific surface area of the obtained material despite negative Cu influence. The tendency of stabilization and agglomerate size rising with the time for Cu and Zr-modified catalysts were traced by dynamic light scattering (DLS) measurements. The observed optical characteristics suggest that Cu compensated the broadening of band gap caused by Zr loading. Crystal structure of obtained photocatalysts was explored by XRD; morphological data and particle size were obtained by SEM. EDX was used for Zr and Cu content determination. Cu K-edge extended X-ray absorption fine structure (EXAFS) and X-ray absorption near edge structure (XANES) analytical techniques were used to investigate the local Cu neighbourhood in the samples and to identify copper coordination and valence state of copper species in the synthesized nanocomposites.
COBISS.SI-ID: 6066202
In this study smart-removal magnetic nanocomposites are developed in an attempt to decrease the band gap energy of the catalyst and to enable separation of the catalyst from the wastewater after the process. Ferrite magnetic nanoparticles Co0.5Zn0.25M0.25Fe2O4 (M?=?Ni, Cu, Mn, Mg) (MNPs) are obtained by the co-precipitation method using carboxymethyl cellulose (CMC) as surfactant and NaOH as precipitation agent. Further, the magnetic nanocomposites Co0.5Zn0.25M0.25Fe2O4-TiO2 (anatase) (MNPs-TiO2) are obtained by the TiO2 deposition onto the MNPs using Pluronic P123 as template and tetra butyl titanate (TBOT) as titanium source. This type of photocatalyst can be used under solar light irradiation because of the activation of TiO2 with MNPs in visible light range and can be very easily recovered due to their strong magnetic properties. The MNPs-TiO2 have proven to be very active for the degradation of different dyes, such as methyl orange and methylene blue, under solar light irradiation.
COBISS.SI-ID: 6323226
Titanium dioxide has been widely used as an antimicrobial agent, UV-filter and catalyst for pollution abatement. Herein, surface modifications with selected transition metals (Me) over colloidal TiO2 nanoparticles and immobilization with a colloidal SiO2 binder as composite films (MeTiO2/SiO2) on a glass carrier were used to enhance solar-light photoactivity. Colloidal TiO2 nanoparticles were modified by loading selected transition metals (Me = Mn, Fe, Co, Ni, Cu, and Zn) in the form of chlorides on their surface. They were present primarily as oxo-nanoclusters and a portion as metal oxides. The structural characteristics of bare TiO2 were preserved up to an optimal metal loading of 0.5 wt%. We have shown in situ that metal-oxo-nanoclusters with a redox potential close to that of O2/O2˙- were able to function as co-catalysts on the TiO2 surface which was excited by solar-light irradiation. The materials were tested for photocatalytic activity by two opposite methods; one detecting O2˙- (reduction, Rz ink test) while the other detecting ˙OH (oxidation, terephthalic acid test). It was shown that the enhancement of the solar-light activity of TiO2 by the deposition of transition metal oxo-nanoclusters on the surface depends strongly on the combination of the reduction potential of such species and appropriate band positions of their oxides. The latter prevented excessive self-recombination of the photogenerated charge carriers by the nanoclusters in Ni and Zn modification, which was probably the case in other metal modifications. Overall, only Ni modification had a positive effect on solar photoactivity in both oxidation and reduction reactions.
COBISS.SI-ID: 6369818