Mesoporous TiO2 Powders Research Articles

Natural sensitizers-mesoporous TiO2 hybrid nanomaterial for future optoelectronic applications

Optoelectronics deals with the design and development of electronic devices including photodetector (PD), solar cells and LEDs for light detection, generation and application for a variety of purposes. It includes X-rays, Gamma rays, Infrared, Ultraviolet and Visible light. In the current work, we developed a self-powered and efficient UV–Visible PD by sensitizing mesoporous TiO2 powder with a natural sensitizer Ficus Benghalensis (Banyan) and Rubia Cordifolia (Manjishtha). Prominent enhancement of visible light absorption was noted due to sensitizers as compared to pure TiO2 with the decrease in band gap from 3.13 eV to 3.01 eV. TiO2 photoanodes fabricated with and without dye loading were characterized using XRD, FESEM and UV–Visible and FTIR spectroscopy and used to fabricate a PD device with an active area of 0. 25 cm2. At zero bias, the Banyan-loaded TiO2 PD (B-TiO2) demonstrates enhanced photo response by nearly three times than Manjishtha-loaded PD (M-TiO2). At zero bias voltage, the PD (B-TiO2) displayed very high photosensitivity (8665), Dark current density (126 nA), Photocurrent density (158 µA), Photoresponsivity (1.88 mA/W), Rise time (0.31S) and Decay time (0.35S), respectively. Therefore, the use of novel dye for electricity generation in this study opens new routes to design future optoelectronics devices.

PHOTOCATALYTIC ACTIVITY OF MESOPOROUS TiO2 (ANATAS) IN THE REACTION OF HYDROGEN RELEASE FROM AQUEOUS-ETHANOLIC MIXTURE

Samples of mesoporous nanocrystalline titanium dioxide (anatase with a crystallite size of about 10 nm) were obtained by a modified sol-gel method in the presence of a template of dibenzo-18-crown-6 and small additives of surfactant (dodecylmethylethylammonium bromide) or ions of lanthanum (III) in butyl alcohol in combination with hydrothermal treatment at 175 °C for 24 hours followed by calcination in air at 500 °C for 4 hours. The photocatalytic activity of the obtained TiO2 samples was investigated in a model reaction of the photocatalytic release of H2 from an aqueous-ethanol mixture. It was found that in all cases the use of hydrothermal treatment significantly increases the photoactivity of the obtained sample, which in some cases is more than 3-4 times higher than the corresponding characteristic for commercial photocatalyst Evonik P25. The key effect of hydrothermal treatment on the increase of photoactivity of the samples is probably the consequence of a drastic increase in the treated samples of pore volume and diameter, as well as a decrease in the size of anatase crystallites. These changes (along with a significant increase in the specific surface area) are greater for samples obtained in the presence of La3+ ions. It is shown that samples of TiO2 microspheres obtained at the same concentrations of reagents in the reaction mixture show slightly higher photocatalytic activity than the corresponding lanthanum-stabilized samples of mesoporous TiO2 powders (micrometer-scale particles are not formed in the presence of lanthanum (III) ions). However, with an increasing concentration of reagents in the reaction mixture, the photocatalytic activity has the sample containing lanthanum. Probably, this can be explained by the high textural characteristics of the TiO2 sample in combination with the peculiarities of its morphology - the formation of secondary nanoparticles of agglomerated formations and the influence of La3+ ions. It is worth noting that the photocatalytic activity of TiO2 samples prepared in the presence of La3+ ions reduces as their specific surface area decreases.

Experimental and computational insights into the aminopropylphosphonic acid modification of mesoporous TiO2 powder: The role of the amine functionality on the surface interaction and coordination

Recently, interest has been directed towards the grafting of metal oxides with organophosphonic acids bearing terminal amine groups to extend the functionality and applicability of these materials. Previous reports mainly focus on the application perspective, while a detailed characterization of the surface properties at the molecular level and the correlation with the synthesis conditions are missing. In this work, mesoporous TiO2 powder is grafted with 3-aminopropylphosphonic acid (3APPA) under different concentrations (20, 75, 150 mM) and temperatures (50, 90 °C) and compared with propylphosphonic acid (3PPA) grafting to unambiguously reveal the impact of the amine group on the surface properties. A combination of complementary spectroscopic techniques and Density Functional Theory-Periodic Boundary Conditions (DFT/PBC) calculations are used. At 90 °C and high concentrations, lower modification degrees are obtained for 3APPA compared to 3PPA, due to amine-induced surface interactions. Both X-ray Photoelectron Spectroscopy (XPS) and Diffuse Reflectance Infrared Fourier Transform (DRIFT) spectroscopy reveal that both NH2 and NH3+ groups are present, with also contributions of NH2 groups involved in hydrogen bonding interactions. A similar ratio of NH2/NH3+ (65:35) is obtained irrespective of the modification conditions, suggesting similar relative contributions of different surface conformations. Calculated adsorption energies from DFT calculations on 3APPA adsorption on anatase (101) in relation to the water coverage reveals a coexistence of various structures with the amine group involved in intra-adsorbate, inter-adsorbate and adsorbate–surface interactions. Further validation is obtained from the strong overlap of different 31P environments represented by the broad band (35-12 ppm) in experimental 31P Nuclear Magnetic Resonance (NMR) spectra and calculated 31P chemical shifts of all modelled monodentate and bidentate structures. Structures related to the tridentate binding mode are not formed due to geometric restrictions of the anatase (101) facet applied as model support in the calculations. Nevertheless, they could be present in the experimental samples as they are composed of anatase (representing multiple crystal facets) and an amorphous titania fraction.

Mesoporous TiO2 from Metal-Organic Frameworks for Photoluminescence-Based Optical Sensing of Oxygen

Metal−organic frameworks (MOFs) are a class of porous coordination networks extraordinarily varied in physicochemical characteristics such as porosity, morphologies, and compositions. These peculiarities make MOFs widely exploited in a large array of applications, such as catalysis, chemicals and gas sensing, drug delivery, energy storage, and energy conversion. MOFs can also serve as nanostructured precursors of metal oxides with peculiar characteristics and controlled shapes. In this work, starting from MIL125-(Ti), a 1,4-benzenedicarboxylate (BDC)-based MOF with Ti as metallic center, mesoporous TiO2 powders containing both anatase and rutile crystalline phases were produced. A challenging utilization of these porous MOF-derived Ti-based oxides is the optically-based quantitative detection of molecular oxygen (O2) in gaseous and/or aqueous media. In this study, the photoluminescence (PL) intensity changes during O2 exposure of two MOF-derived mixed-phase TiO2 powders were probed by exploiting the opposite response of rutile and anatase in VIS-PL and NIR-PL wavelength intervals. This result highlights promising future possibilities for the realization of MOF-derived doubly-parametric TiO2-based optical sensors.

Sol-gel template synthesis of mesoporous carbon-doped TiO2 with photocatalytic activity under visible light

Mesoporous TiO2 powders with an anatase framework were synthesized through surfactant-assisted template method. The concentrated titania sol (7-8 wt.%) prepared from TiCl4 as a precursor was used in this synthesis. The soluble triblock copolymer Pluronic F127 was employed as a structure-directing agent and a carbon precursor to fabricate the carbon-doped mesoporous titania. The synthesized powders were characterized by XRD, HRTEM, Raman spectroscopy, UV-Vis reflectance spectroscopy, N2 adsorption/desorption and TG/DSC methods. The mesoporous titania annealed at 350°C was shown to have a high specific surface area up to 192 m2/g and a narrow pore size distribution. After annealing, carbon species in graphitic form were detected in the template-prepared TiO2 samples using Raman spectroscopy measurements. The photocatalytic performance of the samples was characterized in the process of Rhodamine B decomposition under visible light irradiation. The enhanced visible light photocatalytic efficiency of the template-prepared TiO2 powders as compared with that of Degussa P25 can be attributed to the associated effects of high specific surface area, pure anatase crystalline structure and carbon doping.

Facile synthesis of tunable carbon modified mesoporous TiO2 for visible light photocatalytic application

In this paper, we describe a simple and novel approach for preparing tunable carbon-modified mesoporous TiO2 photocatalysts by combining the in-situ carbonization of PAA-Ti/TiO2, hydrothermal reaction process and post-calcination treatment. The synthesized carbon-modified mesoporous TiO2 powders were of high crystallinity, large specific surface area and good visible light response. The carbon species were formed by the carbonization of polyacrylate (PAA). The presence of carbonates was subsequently confirmed by the XPS spectra, which significantly narrow down the band gap of TiO2. The organic group in polyacrylate served as the carbon source and carbon resulted from in-situ carbonization treatment could help to inhibit the excessive growth of TiO2 grain and enlarge the pore structure of TiO2. The amount of carbon species could be feasibly modulated by adjusting the post-calcination temperature and the surface area of the photocatalyst was enlarged further after the partial removal of carbon species. The carbon-modified mesoporous TiO2 powders exhibit excellent reproducibility and photocatalytic performance under visible light irradiation.

Synthesis and characterization of efficient TiO2 mesoporous photocatalysts

Mesoporous TiO2 powder with large surface area and high porosity was prepared via template-free method of heat-stimulated oxidizing destruction of TiC by HNO3. Anatase crystalline phase of as-prepared and annealed at 200−400°C titania was confirmed by XRD technique. Surface nitrate-nitro groups responsible for high adsorption capacity of the TiO2 powders were studied by FTIR spectroscopy. The annealing temperature can be used as a factor for regulation of titania morphology and structural properties. The rise in the annealing temperature higher than the temperature of nitrate-nitro groups decomposition induces the growth of TiO2 crystallites, decreasing porosity and surface area, the drop of adsorption capacity, and improving photocatalytic activity under UV irradiation.

Evaluation of photoconductive and photoelectrochemical properties of mesoporous nanocrystalline TiO2 powders and films prepared in acidic and alkaline media

Nanocomposite TiO2 powders were prepared via hydrothermal route using titanium(IV) butoxide as starting material at different pH media. In particular, three alkaline media composed of ammonium carbonate, ammonium bicarbonate and urea were used as modulators of the TiO2 nanostructure. Besides, sulfuric acid was also used succeeding an acidic environment for the growth of TiO2 nanoparticles. The structural properties of powders made either in acidic or alkaline environment were examined with microscopy techniques (FE-SEM), X-ray diffraction patterns (XRD), porosimetry (BET) and FTIR spectroscopy. TiO2 films were fabricated by suitably modifying the synthesized powders in the form of easily handled pastes. The powders were evaluated to their photoconductivity properties while films were sensitized with N719 ruthenium dye and employed as photoanodes in quasi-solid state dye sensitized solar cells (DSSCs). The cells were characterized in terms of their electrical and electrochemical characteristics using impedance spectroscopy. The overall performance of the solar cells employing TiO2 films prepared in acidic or alkaline environment was higher than that recorded for commercially obtained TiO2 powder (Degussa-P25) with a maximum difference of 16% in the case of TiO2 made in acidic environment.

Mesoporous TiO2 powders as host matrices for iron nanoparticles. Effect of the preparation procedure and doping with Hf

The aim of the current investigation is to follow the formation of iron phase in mesoporous nanocrystalline titania and Hf-doped titania powders and its influence on the physicochemical and catalytic properties of the obtained materials. The parent host matrices were synthesized by using either template-assisted hydrothermal approach or homogeneous precipitation with urea. The iron modifications were prepared by incipient wetness impregnation with Fe(NO3)3.9H2O. Nitrogen physisorption, X-ray diffraction, TEM analysis, Moessbauer spectroscopy, UV–Vis spectroscopy and TPR with hydrogen were the techniques used for samples characterization and their catalytic behaviour was studied in methanol decomposition and ethyl acetate oxidation as catalytic tests. The hydrothermal treatment, the iron modification and the doping with Hf lead to the appearance of a significant absorption in the visible region for the studied samples, which together with the red shift of the absorption edge could be advantageous because of increased yield of photogenerated electron–hole pairs. The presence of very highly dispersed and uniform iron oxide particles with sizes below 4 nm and superparamagnetic behaviour are most beneficial for the catalytic activity in ethyl acetate total oxidation. On the other hand, the iron introduction retards the methanol conversion by blocking some of the supports active sites and alone or together with Hf changes the selectivity to predominant methane formation.

Synthesis of mesoporous TiO2 structures through P123 copolymer as the structural directing agent and assessment of their performance in dye-sensitized solar cells

A novel and efficacious strategy was implemented for creation of mesoporous TiO2 films and powder through an integration of sol–gel and evaporation-induced self-assembly (EISA) processes aided by triblock Pluronic P123. A mesoporous crack-free thin film with virtual thickness of 300nm was attained under 10% relative humidity aging, for 72h at the low temperature of 5°C. Further, the TiO2 film with porous structure has been formed from conventional paste, exploiting as-prepared mesoporous titania powder. The X-ray Diffraction (XRD) of synthesized mesoporous powder disclosed formation of anatase phase as well as rutile phase, in such a manner that the latter constituted a very small minority. Moreover, Brunauer–Emmett–Teller (BET) and Barrett–Joyner–Helenda (BJH) proved that the isotherm pertaining to synthesized powder implies a combination of types II and IV which are related to mesoporous material with average pore size of 5.8nm and BET surface area of 114m2/g. Owing to the quantum size effect, diffuse reflection spectroscopy of prepared mesoporous TiO2 powder denoted a blue shift by comparison with that of bulk TiO2. The mesoporous TiO2 film which has been prepared under optimized circumstances, possesses appropriate microstructural and optical properties so that it can be utilized for dye-sensitized solar cell (DSSC) applications. In order to delve profoundly into the effect of TiO2 thin film, two types of monolayer and doublelayer DSSCs were made. In light of the achieved results, the doublelayer cell indicated superior power conversion efficiency and short circuit current density of 8.05% and 18.27mA/cm2, respectively.

Photocatalytic degradation of p-nitrophenol and methylene blue using Zn-TCPP/Ag doped mesoporous TiO2 under UV and visible light irradiation

In this study, Ag-doped mesoporous TiO2 powder was prepared via a sol–gel route with Pluronic P123 as template and then was modified with zinc(II) tetrakis(4-carboxyphenyl)porphyrin. The catalysts were characterized by X-ray diffraction, diffuse reflectance spectroscopy, Fourier transform infrared (FT-IR), scanning electron microscopy, N2 sorption experiments (BET), X-ray fluorescence analysis, and inductively coupled plasma spectroscopy. The photocatalytic activities of Ag-doped mesoporous TiO2 and Zn-TCPP/Ag-doped mesoporous TiO2 were evaluated using methylene blue and p-nitrophenol as pollutant compounds under UV and visible light irradiation. The results show that Zn-TCPP/Ag-doped mesoporous TiO2 have higher activity than Ag-doped mesoporous TiO2 under visible light irradiation, but its activity is lower under UV light irradiation.

Evaluation of the anatase/rutile phase composition influence on the photocatalytic performances of mesoporous TiO2 powders

We investigated the influence of the microstructure, texture and the relative amount of anatase and rutile phases on the photoelectrocatalytic H2 evolution over mesoporous TiO2 (m-TiO2). This study was carried out by means of ex-situ powder X-ray diffraction (XRPD), N2 physisorption, transmission electron microscopy (TEM), and photoelectrolysis measurements. The synthesis of nanocrystalline TiO2 powders with different anatase/rutile weight ratios was successfully approached by evaporation-induced self assembly (EISA) method simply varying the volume amount of TiCl4 and Ti(OBu)4 (acid–base pair) as metal precursors. In particular, m-TiO2 with anatase/rutile weight ratios similar to commercial TiO2 (P25) was obtained. The microstructure, texture and photocatalytic properties toward hydrogen evolution reaction (HER) of the as-synthesized TiO2 were compared with commercial P25. Interestingly, the m-TiO2 with a high surface area of 196 m2/g, uniform pore size and 87/13 anatase/rutile weight ratio, showed a significant increase in the photoactivity with respect to the powders richer in either anatase or rutile phases. Furthermore, it was claimed that the crystallinity and specific surface area play a key role on the photocatalytic activity of the synthesized m-TiO2 samples.

Mesoporous TiO2 nanoparticles for highly sensitive solid-phase microextraction of organochlorine pesticides

Mesoporous TiO2 nanoparticles were synthesized with the hydrothermal method and characterized by powder X-ray diffraction (PXRD) and transmission electron microscope (TEM). Then a superior solid-phase microextraction (SPME) fiber was fabricated by sequentially coating the stainless steel fiber with silicone sealant film and mesoporous TiO2 powder. The developed fiber possessed a homogeneous surface and a long life-span up to 100 times at direct immersing (DI) extraction mode. Under the optimized conditions, the extraction efficiencies of the self-made 17μm TiO2 fiber for six organochlorine pesticides (OCPs) were higher than those of the two commercial fibers (65μm PDMS/DVB and 85μm PA fibers) which were much thicker than the former. As for analytical performance, low detection limits (0.08–0.60ngL−1) and wide linearity (5–5000ngL−1) were achieved under the optimal conditions. The repeatabilities (n=5) for single fiber were between 2.8 and 12.3%, while the reproducibilities (n=3) of fiber-to-fiber were in the range of 3.7–15.7%. The proposed fiber was successfully applied to the sensitive analysis of OCPs in real water samples and four of the six analytes were detected from the rainwater and the lake water samples.

A floating macro/mesoporous crystalline anatase TiO2ceramic with enhanced photocatalytic performance for recalcitrant wastewater degradation

A macro/mesoporous anatase TiO2 ceramic floating photocatalyst has been successfully synthesized using highly thermally stable mesoporous TiO2 powder as a precursor, followed by a camphene-based freeze-casting process and high-temperature calcinations. The ceramics are characterized in detail by X-ray diffraction, Raman spectra, scanning electron microscopy, transmission electron microscopy and N2 adsorption-desorption isotherms. The results indicate that the TiO2 ceramics present hierarchical macro/mesoporous structures, which maintain high porosity and high compressive strength at the optimal sintering temperature of 800 °C. The ordered mesoporous TiO2 network still possesses high thermal stability and inhibits the anatase-to-rutile phase transformation during calcinations. The obtained ceramics exhibit good adsorptive and photocatalytic activity for the degradation of octane and rhodamine B, and the total organic carbon removal ratio is up to 98.8% and 98.6% after photodegradation for 3 h, respectively. The roles of active species in the photocatalytic process are compared using different types of active species scavengers, and the degradation mechanism is also proposed. Furthermore, the ceramics are recyclable, and no clear changes are observed after ten cycles. In addition, the ceramics are also active in the photodegradation of phenol, thiobencarb, and atrazine. Therefore, these novel floating photocatalysts will have wide applications, including the removal of floating organic pollutants from the wastewater surfaces or the removal of soluble organic pollutants from wastewater.

Hydrogen evolution from aqueous methanol solution on mesoporous titania prepared by a process combining evaporation induced self-assembly and spray pyrolysis

Mesoporous TiO2 powders were prepared in 1min from an aqueous mixture of chelated complex titanium precursor and tri-block copolymer by using a process combining evaporation induced self-assembly (EISA) and spray pyrolysis. Photocatalytic activity was evaluated by measuring the rate of hydrogen evolution from methanol solution. The prepared powders were mainly anatase phase and had worm-like pores. Crystallite size was in the range from 7.8 to 18.6nm in diameter. The mesoporous TiO2 powders calcined at 823K had surface area of 144m2g−1 and high pore volume of 0.33cm3g−1. Pore size distribution was also narrow. In addition, it had high light absorption intensity below 350nm. The rate of hydrogen evolution was by a factor of six higher than the rate measured with commercial nano-sized TiO2 powder (Degussa P-25). Unique structural and optical properties, which were mainly originated from our new combined process of EISA and spray pyrolysis, contributed to the enhanced rate of hydrogen evolution.

Increases in solar conversion efficiencies of the ZrO2 nanofiber-doped TiO2 photoelectrode for dye-sensitized solar cells

In this paper, in order to improve the efficiency of dye-sensitized solar cells, we introduced zirconia [ZrO2] nanofibers into a mesoporous titania [TiO2] photoelectrode. The photoelectrode consists of a few weight percent of ZrO2 nanofibers and a mesoporous TiO2 powder. The mixed ZrO2 nanofibers and the mesoporous TiO2 powder possessed a larger surface area than the corresponding mesoporous TiO2 powder. The optimum ratio of the ZrO2 nanofiber was 5 wt.%. The 5 wt.% ZrO2-mixed device could get a short-circuit photocurrent density of 15.9 mA/cm2, an open-circuit photovoltage of 0.69 V, a fill factor of 0.60, and a light-to-electricity conversion efficiency of 6.5% under irradiation of AM 1.5 (100 mW/cm2).

Bulky mesoporous TiO2 structure

We report a bulky mesoporous TiO2 structure fabricated by direct consolidation of mesoporous TiO2 powder. The mesoporous TiO2 powder with an interparticular porosity, which synthesized by a surfactant-mediated sol–gel method, was consolidated by spark plasma sintering at 350–600 °C. A mesoporous structure in the sintered body was revealed by N2 adsorption–desorption isotherms, and the maximum surface area of ∼131 m2 g−1 was obtained with a porosity of ∼44%. Linear grain growth of the primary TiO2 particle size was observed in the bulky mesoporous structure, and the effects of open pores on the grain growth kinetics were discussed.

Low Temperature Synthesis and Visible Light Driven Photocatalytic Activity of Highly Crystalline Mesoporous TiO<SUB>2</SUB> Particles

Mesoporous TiO2 powder materials with a high crystallinity have been prepared by evaporation induced self assembly (EISA) process using titanium tetraisopropoxide (TTIP) and pluronic P123 surfactant (EO20PO70EO20) as titanium source and structure-directing reagent, respectively. The prepared materials were characterized by low and wide-angle X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), optical absorption, and N2 adsorption-desorption experiments. The crystallinity of the materials was controlled by varying the calcination temperature. The resulting TiO2 materials showed highly crystalline structure with uniform particle size which increases from 11.8 to 23.8 nm with increasing the calcination temperature from 400 to 600 degrees C, respectively, whereas the specific surface area decreases from 125 to 40 m2/g. TEM and XRD results revealed that the calcination temperature of 600 degrees C is the best condition to obtain highly crystalline mesoporous TiO2. The photocatalytic activity of the TiO2 mesoporous materials with different crystallinity and textural parameters has been studied in the decomposition of methylene blue (MB) dye molecules under visible light irradiation. Among the mesoporous TiO2 materials studied, the material with the highest crystallinity, prepared at 600 degrees C, showed the best photocatalytic performance in the decomposition of MB under visible light in a short time.

SYNTHESIS OF MESOPOROUS TITANIA BY POTATO STARCH TEMPLATED SOL-GEL REACTIONS AND ITS CHARACTERIZATION

Mesoporous titania powders with high-order crystalline building blocks had been synthesized through the sol-gel process using potato starch gel template. Internal spongelike pore structure of starch gel template was generated by heating the starch granules at 95 °C in water solution and freezing the starch gel at -15 °C. The synthesis routes were performed by immersing the starch gel template for 4 days into the white colloidal solution of TiO2 nanoparticles, which were prepared by hydrolyzing titanium (IV) tetraisopropoxide (TTIP) in ethanol at pH 1. Mesoporous TiO2 powders were obtained by two different ways of template removal, performed by calcination of the TiO2-starch composites at 600 °C for 4 h or combination of extraction with ethanol-HCl (2:1) at 80 °C and calcination at 500 °C for 4 h. Fourier Transform Infra Red (FT-IR) spectra shows both of template removal methods result in decreasing of characteristic vibrational band of the starch hydrocarbon on the resulted TiO2 powders. The X-Ray Diffraction (XRD) pattern imply that the concentrations of starch gel template influence the anatase crystallite peaks intensity of the synthesized TiO2 powders. TiO2 templated by 20% of starch sponges gel has highest intensity of anatase crystallite. Scherrer calculation inidicated that anatase particle size has nanoscale dimmension up to 12.96 nm. The nano-architecture feature of mesoporous TiO2 scaffolds was also evaluated by the Scanning Electron Microscope (SEM). It is shown that mesoporous TiO2 framework consist of nanocrystalline TiO2 particles as buiding blocks. The N2 adsorption-desorption isotherm curves assign that TiO2 powder resulted from extraction-calcination route has higher mesoporosity than that of only calcinated. The synthesized mesoporous TiO2 powder exhibits high Brunauer-Emmet-Teller (BET) specific surface area up to 65.65 m2/g. Keywords: mesoporous TiO2, potato starch, template

Photocatalytic Degradation of Acetaldehyde on Mesoporous TiO2: Effects of Surface Area and Crystallinity on the Photocatalytic Activity

Mesoporous TiO2 powder and films with worm-like channels were synthesized by an evaporation-induced self-assembly approach. The as-prepared samples were calcined at different temperature to investigate the effect of calcined temperature on the mesostructure and the photocatalytic activity. Acetaldehyde photodegradation in gas phase was employed to evaluate the photocatalytic activity of mesoporous TiO2. Results showed that all the calcined powder samples exhibited higher photocatalytic activities than that of Degussa P25. The sample calcined at 400C, which showed higher activity than other samples, possessed a homogeneous pore diameter of about 6.0 nm and an 11.0 nm crystalline anatase pore wall, as well as large surface area of 117 m2/g. It was speculated that two factors of surface area and crystallinity affected the photocatalytic activity of mesoporous TiO2 photocatalyst. The mesoporous TiO2 films fabricated by spin-coating also had high photocatalytic activities.