Commercial TiO2 Photocatalyst Research Articles

Silica supported TiO2 nanostructures for highly efficient photocatalytic application under visible light irradiation

Titanium dioxide decorated silica nanospheres have been synthesized by a simple wet chemical approach. X-ray diffraction, electron microscopy and energy dispersive X-ray analysis revealed that anatase phase of TiO2 nanostructures, with exposed {001} and {101} facets, are anchored onto the amorphous silica spheres of ∼60nm diameter. The photocatalytic activity of the sample under visible light irradiation was examined. It is found that photocatalytic efficiency of the material is better than commercial P25 TiO2 photocatalyst and the result is attributed to the unique synergistic effect of SiO2–TiO2 nanocomposite structure resulting enhanced charge separation and charge transfer.

Effect of calcination temperatures on the photocatalytic activities of commercial titania nanoparticles under solar simulator irradiation

In this study, the effect of calcination temperatures on the photocatalytic activity of commercial TiO2 photocatalysts (Evonik P25, Evonik P90, Hombikat UV100, Hombikat N100) was evaluated for degradation and removal of 2,4-dichlorophenoxyacetic acid (2,4-D) herbicide under solar simulator irradiation. The calcined samples were prepared by heating commercial TiO2 photocatalysts at 573 or 773 K for 4 hours. It was confirmed that before calcination treatment, the P25 TiO2 showed similar activity to the P90 TiO2, which activity was higher than those of Hombikat UV100 and N100 TiO2. The activity of P25 and P90 was reduced when the photocatalysts were calcined at 573 K and 773 K. On the other hand, the Hombikat catalysts showed an improved activity with the increase of calcination temperatures.

SiO2/TiO2 double-shell hollow particles: Fabrication and UV–Vis spectrum characterization

Well-defined SiO2/TiO2 double-shell hollow particles (STDSHPs) were successfully fabricated by a sol–gel method with avoiding the particle aggregations and the generation of freestanding TiO2 particles. Comparing with the conventional solid TiO2 particles, STDSHPs showed a novel hollow structure, a much smaller TiO2 grain size (9nm), and a larger specific surface area (113m2/g). In the UV–vis spectrum characterizations, STDSHPs showed significant light harvesting capability in both UV- and visible-light range. STDSHPs also showed stronger per-weight UV absorbance capability than solid TiO2 particles and commercial TiO2 photocatalyst P25, which could be attributed to their novel hollow structure—and thus the absence of light-inaccessible TiO2 particles. Moreover, we analyzed the narrowed band-gap of STDSHPs by the Brus’ effective-mass model (EMM).

Selective Activation of C=C Bond in Sustainable Phenolic Compounds from Lignin via Photooxidation: Experiment and Density Functional Theory Calculations

Lignocellulosic biomass can be converted to high-value phenolic compounds, such as food additives, antioxidants, fragrances and fine chemicals. We investigated photochemical and heterogeneous photocatalytic oxidation of two isomeric phenolic compounds from lignin, isoeugenol and eugenol, in several nonprotic solvents, for the first time by experiment and the density functional theory (DFT) calculations. Photooxidation was conducted under ambient conditions using air, near-UV light and commercial P25 TiO2 photocatalyst, and the products were determined by TLC, UV-Vis absorption spectroscopy, HPLC-UV and HPLC-MS. Photochemical and photocatalytic oxidation of isoeugenol proceeds via the mild oxidative "dimerization" to produce the lignan dehydrodiisoeugenol (DHDIE), while photooxidation of eugenol does not proceed. The DFT calculations suggest a radical stepwise mechanism for the oxidative "dimerization" of isoeugenol to DHDIE as was calculated for the first time.

Visible light TiO2 photocatalysts assessment for air decontamination

Different visible light responses of commercial TiO2 photocatalysts are assessed for their application in air decontamination. To do that the modified TiO2 catalysts were immobilized on borosilicate glass plates according to a dip coating method. Then, the photocatalytic performance of these plates was evaluated in a continuous gas flat plate photoreactor irradiated with visible light lamps using two representative air pollutants: nitrogen oxide and acetaldehyde. Working under visible light, the modified TiO2 catalysts were compared by means of efficiency parameters: the true quantum efficiency, which relates the moles of degraded pollutant with the moles of the absorbed photons, and the apparent photonic efficiency, which relates the moles of degraded pollutant with the moles of incident photons. Also, the photocatalytic pollutants degradation by immobilized modified TiO2 could be related with their optical properties, finding a clear correlation between them. These results are useful to decide which TiO2 will be more efficient for a full scale air decontamination process under visible light illumination.

Photocatalytic reduction of acetophenone in membrane reactors under UV and visible light using TiO2 and Pd/TiO2 catalysts

A photocatalytic membrane reactor, as a novel method, was tested in the hydrogenation of acetophenone to produce phenylethanol, a compound of wide industrial interest. Water as solvent and formic acid as hydrogen and electron donor, under UV and visible light irradiation, have been employed to develop a green and sustainable process. It was found that use of a membrane reactor improves the efficiency of the photocatalytic reaction compared to a batch reactor (productivity 4.44mgg−1h−1 vs. 2.96mgg−1h−1) thanks to the extraction of phenylethanol in the organic extracting phase, simultaneously to the reaction, thus enhancing the process selectivity. Different methods for the substrate addition in the membrane photoreactor were tested finding the best performance when the acetophenone was used as both solvent and reactant (substrate). A simple modification of commercial TiO2 photocatalyst by doping it with Pd, by deposition precipitation method, improved five times its photocatalytic activity in the photocatalytic membrane reactor under visible light irradiation (productivity 22.0mgg−1h−1).

Photocatalytic Performance of a Nd-SiO2-TiO2 Nanocomposite for Degradation of Rhodamine B Dye Wastewater.

The photocatalytic performance of a novel Nd-SiO2-TiO2 nanocomposite catalyst prepared by a sol-gel method was examined in the degradation of Rhodamine B (RhB), a notorious organic compound present in dye wastewaters. The prepared samples were characterized by low-temperature N2 adsorption, X-ray diffraction (XRD), transmission electron microscopy (TEM) and UV-vis diffuse reflectance spectroscopy (DRS). Fourier-transform infrared (FT-IR) spectroscopic analysis indicated the enhanced chemical bonding of O--Ti and O--Ti--O with introduction of Nd and SiO2 dopant species into TiO2. The Nd-SiO2-TiO2 nanocomposite was found to exhibit a much higher photo- catalytic activity toward the decomposition of RhB under both UV and visible light irradiation as compared to a commercial TiO2 photocatalyst. The photodegradation efficiency of RhB (5 mg/L) was greater than 93% under visible light irradiation after 90 min. Addition of SiO2 was shown to not only inhibit crystal growth and TiO2 anatase-to-rutile phase transformation, but also enhance the adsorption of organic compounds. Nd doping has been suggested for slowing down the radiative recombination of photo-generated electrons and holes in TiO2, extending the photocatalyst light response to the visible region. The synergetic effects between Nd-SiO2 and TiO2 are described; the prepared Nd-SiO2-TiO2 represents a noteworthy contribution to the study of pollutant degradation in dye wastewaters.

Completely oriented anatase TiO2 nanoarrays: topotactic growth and orientation-related efficient photocatalysis.

A TiO2 film has been facilely grown on a Ti foil via a general and simple acid vapor oxidation (AVO) strategy. Based on detailed characterization by using X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM), we found that the TiO2 film was composed of anatase nanoarrays highly oriented along their <001> direction, resulting in a large exposed {001} top surface on the film. The growth mechanism based on a topotactic transformation was proposed according to a careful study of time-dependent experimental results. Resulting from the evaluation of photocatalytic performance compared with a commercial TiO2 photocatalyst (Degussa P25), the as-prepared oriented anatase TiO2 film showed higher efficiency for degradation of atrazine and acid orange II (AOII). The performance of photocatalysis is highly relevant to the preferential orientation. The efficient photocatalysis could be attributed to the highly reactive {001} facets on the anatase nanoarrays with super-hydrophilicity.

Synthesis of rare earth doped TiO2 nanorods as photocatalysts for lignin degradation.

A two-step process is developed to synthesize rare earth doped titania nanorods (RE-TiO2 NRs) as photocatalysts for efficient degradation of lignin under simulated sunlight irradiation. In this approach, protonated titanate nanotubes with layered structures were first prepared by a hydrothermal approach, and rare earth metal ions were subsequently bound to the negatively charged surface of the synthesized titanate via electrostatic incorporation. The as-synthesized RE-TiO2 NRs after calcination generally showed much higher photocatalytic efficiencies than those of undoped TiO2 NRs or the commercial P25 TiO2 photocatalyst. Using methyl orange (MO) as a probing molecule, we demonstrate that Eu-TiO2 NRs are among the best for degrading MO, with an observed rate constant of 4.2 × 10(-3) s(-1). The La(3+), Sm(3+), Eu(3+) and Er(3+) doped TiO2 NRs also showed higher photocatalytic efficiencies in degrading MO than the commercial P25 TiO2. We further demonstrate that lignin can be photodegraded effectively and rapidly at room temperature under simulated sunlight through two reaction routes, which could be important in controlling ways of lignin depolymerization or the formation of reaction products.

Preparation of Carbon‐Nanotube‐supported TiO2 for Enhanced Dye‐degrading Photocatalytic Activity

Titanium dioxide–carbon nanotube (TiO2‐CNT) nanocomposites were successfully synthesized by a sol–gel method. The prepared TiO2‐CNT samples were characterized by transmission electron microscopy (TEM), X‐ray photoelectron spectroscopy (XPS), and X‐ray diffraction (XRD). The photocatalytic activity of the samples was tested by photodegradation of methylene blue (MB) and methyl orange (MO) in aqueous solution under UV‐light irradiation. In the photocatalytic results, the TiO2‐CNTs, as compared to the pristine TiO2 and commercial P25 TiO2 photocatalysts, exhibited the fastest degradation performance in both dye solutions. The TiO2‐CNTs’ apparent rate constants were 0.0232 and 0.0214 min–1 in the MB and MO solutions, respectively, both of which are approximately 5 times greater than that for the commercial P25 TiO2 (MB: 0.0046 min–1, MO: 0.0043 min–1). And as for the estimated electron‐transfer resistance (Rct) results from the ac impedance spectra, the values increased in the following order: TiO2‐CNT &lt; P25 TiO2 &lt; pristine TiO2 , indicating that CNTs can serve as electron‐transmitting paths, thus suppressing the recombination rate of photogenerated electron/hole pairs. Moreover, the degree of photodegradation inhibition was insignificant in the presence of interfering anion species (1000‐fold).

Fe2 O3 -TiO2 nanocomposites for enhanced charge separation and photocatalytic activity.

Photocatalysis provides a cost effective method for both renewable energy synthesis and environmental purification. Photocatalytic activity is dominated by the material design strategy and synthesis methods. Here, for the first time, we report very mild and effective photo-deposition procedures for the synthesis of novel Fe2 O3 -TiO2 nanocomposites. Their photocatalytic activities have been found to be dramatically enhanced for both contaminant decomposition and photoelectrochemical water splitting. When used to decompose a model contaminant herbicide, 2,4-dichlorophenoxyacetic acid (2,4-D), monitored by both UV/Vis and total organic carbon (TOC) analysis, 10% Fe-TiO2 -H2 O displayed a remarkable enhancement of more than 200 % in the kinetics of complete mineralisation in comparison to the commercial material P25 TiO2 photocatalyst. Furthermore, the photocurrent is nearly double that of P25. The mechanism for this improvement in activity was determined using density functional theory (DFT) and photoluminescence. These approaches ultimately reveal that the photoelectron transfer is from TiO2 to Fe2 O3 . This favours O2 reduction which is the rate-determining step in photocatalytic environmental purification. This in situ charge separation also allows for facile migration of holes from the valence band of TiO2 to the surface for the expected oxidation reactions, leading to higher photocurrent and better photocatalytic activity.

Y(IO3)3 as a Novel Photocatalyst: Synthesis, Characterization, and Highly Efficient Photocatalytic Activity

Nonbonding layer-structured Y(IO3)3 was successfully prepared by a simple hydrothermal route and investigated as a novel photocatalyst for the first time. Its crystal structure was characterized by X-ray diffraction, high-resolution transmission electron microscopy, and scanning electron microscopy. The optical absorption edge and band gap of Y(IO3)3 have been determined by UV-vis diffuse reflectance spectra. Theoretical calculations of the electronic structure of Y(IO3)3 confirmed its direct optical transition property near the absorption edge region, and the orbital components of the conduction band and valence band (VB) were also analyzed. The photocatalytic performance of Y(IO3)3 was evaluated by photooxidative decomposition of rhodamine B under ultraviolet light irradiation. It demonstrated that Y(IO3)3 exhibits highly efficient photocatalytic activity, which is much better than those of commercial TiO2 (P25) and important UV photocatalysts BiOCl and BiIO4. The origin of the excellent photocatalytic performance of Y(IO3)3 was investigated by electron spin resonance and terephthalic acid photoluminescence techniques. The results revealed that the highly strong photooxidation ability that resulted from its very positive VB position should be responsible for the excellent photocatalytic performance.

Transition metal oxide loaded ZnO nanorods: Preparation, characterization and their UV–vis photocatalytic activities

A series of transition metal oxides (MOx/ZnO nanorods, where MOx=WO3, CuO and NiO) loaded ZnO catalyst was successfully prepared by a hydrothermal-deposition method. The catalysts were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX), Brunauer–Emmett–Teller (BET) surface area analysis, UV–vis diffuse reflectance spectroscopy (UV–vis DRS), Fourier transform infrared (FTIR) spectroscopy and photoluminescence (PL) spectroscopy. The results showed that the crystallized MOx/ZnO had a hexagonal wurtzite phase with the respective transition metal oxides being attached on ZnO nanorods. The MOx/ZnO photocatalysts with the transition metal oxides, namely WO3 and CuO were responsive to visible light. Photocatalytic activities over pure ZnO and MOx/ZnO catalysts were compared and the observed rate constant (k) values were calculated from the kinetic studies of phenol degradation under UV–vis light irradiation. The extent of degradation of phenol and their mineralization were verified further by HPLC and TOC analyses. 2at% WO3/ZnO displayed the best photocatalytic performance with the highest degradation efficiency (100%) and highest k (0.0135min−1) after 5h irradiation. Moreover, the photoactivity of 2at% WO3/ZnO was found to be higher than those of pure ZnO and commercial TiO2 photocatalyst. Remarkably high UV–vis light photocatalytic activity of WO3/ZnO heterojunction could be explained by inter-semiconductor electron and hole transfer mechanism between the WO3 and that of ZnO nanorods. The evidence for the electron and hole transports between WO3 and ZnO nanorods was obtained by monitoring the PL and PL–Terephthalic acid (TA) measurements.

New nanostructured silica incorporated with isolated Ti material for the photocatalytic conversion of CO2 to fuels

In this work, new nanoporous silica (Korea Advanced Institute of Science and Technology-6 (KIT-6)-dried or KIT-6-calcined) incorporated with isolated Ti materials with different Si/Ti ratios (Si/Ti = 200, 100, and 50) has been synthesized and investigated to establish photocatalytic reduction of CO2 in the presence of H2O vapors. The properties of the materials have been characterized through N2 adsorption/desorption, UV-vis, TEM, FT-IR, and XPS analysis techniques. The intermediate amount of the isolated Ti (Si/Ti = 100) has resulted to be more uniformly distributed on the surface and within the three-dimensional pore structure of the KIT-6 material, without its structure collapsing, than the other two ratios (Si/Ti = 200 and 50). However, titania agglomerates have been observed to have formed due to the increased Ti content (Si/Ti = 50). The Ti-KIT-6 (calcined) materials in the reaction showed higher activity than the Ti-KIT-6 (dried) materials, which produced CH4, H2, CO, and CH3OH (vapors) as fuel products. The Ti-KIT-6 (Si/Ti = 100) material also showed more OH groups, which are useful to obtain a higher production rate of the products, particularly methane, which was even higher than the rate of the best commercial TiO2 (Aeroxide P25, Evonik Industries AG, Essen, Germany) photocatalyst.

Study of gamma irradiation effect on commercial TiO2 photocatalyst

The aim of this work is to understand the effect of gamma irradiation on commercial TiO2 photocatalyst for water treatment applications. Previous studies concluded that gamma-irradiation is able to modify the electronic properties of TiO2 based photocatalysts and consequently their photocatalytic performance. However, there are some discrepancies in the literature where on one hand a significant enhancement of the material properties is reported and on the other hand only a weak effect is observed. In this study a surface effect on TiO2 is confirmed by using low and medium gamma irradiation doses.

Cost-effectiveness analysis to assess commercial TiO2 photocatalysts for acetaldehyde degradation in air

AbstractIn the commercialisation of photocatalytic air purifiers, the performance as well as the cost of the catalytic material plays an important role. Where most comparative studies only regard the photocatalytic activity as a decisive parameter, in this study both activity and cost are taken into account. Using a cost-effectiveness analysis, six different commercially available TiO2-based catalysts are evaluated in terms of their activities in photocatalytic degradation of acetaldehyde as a model reaction for indoor air purification.

Testing methods for antimicrobial activity of TiO2 photocatalyst

In recent years, a lot of commercial TiO2 photocatalyst products have been developed and extensively studied for prospective and safe antimicrobial application in daily life, medicine, laboratories, food and pharmaceutical industry, waste water treatments and in development of new self-cleaning and antimicrobial materials, surfaces and paints. This paper reviews the studies published worldwide on killing microorganisms, methods for testing the antimicrobial activity, light sources and intensities, as well as calculation methods usually used when evaluating the antimicrobial properties of the TiO2-based products. Additionally, some strengths and weaknesses of the available methods for testing the antimicrobial activity of TiO2 photocatalyst products have been pointed out.

Photoelectrocatalytic decomposition of Acid Black 1 dye using TiO2 nanotubes

TiO2 nanotube arrays were prepared by anodization with titanium anode and platinum cathode by electrochemical and sonoelectrochemical technique. The rate of formation of the TiO2 nanotubes by the sonoelectrochemical method is found to be almost twice as fast as the electrochemical method. The photocatalytical activities of TiO2 nanotubes were tested in the photoelectrocatalytical degradation of aqueous solution of a commercial dye Acid Black 1, comparatively with various commercial TiO2 photocatalysts. The results showed that sonoelectrochemically prepared TiO2 tubes exhibited 10% higher photocatalytic performance than the electrochemical prepared ones, and more than 20% higher activity than the other TiO2 samples. Furthermore, the effects of various operating parameters such as dye concentration, temperature and light intensity were also investigated in the photoelectrocatalytic degradation.

Development and photocatalytic activities of TiO2 doped with Ca–Ce–W in the degradation of acid red 1 under visible light irradiation

A stable visible light photocatalyst has successfully been developed by doping titanium dioxide (TiO2) with Ca, Ce, and W. Various combinations were developed and tested. The photocatalyst, when subjected to visible light photocatalytic degradation of C.I. Acid red 1 (AR1) showed an excellent performance in comparison with the most acclaimed commercial TiO2 photocatalyst, Degussa P25. The photocatalytic process with the best developed photocatalyst is “initial-concentration”-dependent, as high initial concentrations of AR1 dye precluded the photon energy from reaching the photocatalyst, and hence reduced its degradation rate. Initial pH of dye solution exerts its influence on the visible light photocatalytic degradation of the dye. High initial pH 10 was detrimental to the process, while the process was controlled by adsorption at lower pH 3. The developed photocatalysts were characterized by X-ray photoelectron spectroscopy, UV–vis diffuse reflectance spectra, X-ray diffraction, N2 physisorption, surface scanning electron microscopy, and fourier transform infra-red spectroscopy. The results showed a red shift in the band gap of the tri-doped TiO2 from 3.2 to 2.94 eV indicating a shift in the onset optical wavelength from 387.19 to 421.43 nm.

130-fold enhancement of TiO2 photocatalytic activities by ball milling

Submicrometer TiO2 particles were prepared by changing the mechanochemical parameters in planetary ball milling. The TiO2 particles before and after milling were characterized by five experimental methods. The photocatalytic activities of the TiO2 particles were evaluated by the photoreduction of an aqueous solution of methylene blue. The activity of milled TiO2 was 136 times that of TiO2 (anatase) before milling and 62 times that of commercial available TiO2 photocatalyst (P25). In addition to the reduction in particle size and increase in specific surface area due to milling, the disorder TiO2, involving amorphous and srilankite phases, significantly increased the catalytic performance.