Room temperature synthesis of Ti-SBA-15 from silatrane and titanium-glycolate and its catalytic performance towards styrene epoxidation

A novel room temperature sol–gel synthesis of Ti-SBA-15 is described using moisture stable silatrane and titanium glycolate precursors, and poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) block copolymer (EO₂₀PO₇₀EO₂₀) as the structure directing agent. Catalyst performance was optimized by systematically investigating the influence of acidity, reaction time and temperature, and titanium loading. Small angle X-ray scattering (SAXS) and transmission electron microscopy (TEM) showed well-ordered 2D mesoporous hexagonal structures, while N₂ adsorption/desorption measurements yielded high surface areas (up to 670 m²/g), with large pore diameters (5.79 nm) and volumes (0.83 cm³/g). Diffuse reflectance UV–visible spectroscopy (DRUV) was found that tetravalent titanium as Ti⁴⁺O₄ tetrahedra were incorporated in the framework through displacement of Si⁴⁺O₄ after calcination (550°C/6 h) to loadings of 7 mol% Ti without perturbation of the ordered mesoporous structure, or decoration by extra-framework anatase containing Ti⁴⁺O₆ octahedra. The catalytic activity and selectivity of styrene epoxidation using hydrogen peroxide (H₂O₂) showed that the conversion of styrene increases significantly at higher titanium contents. The only products of this reaction were styrene oxide and benzaldehyde, with selectivity of 34.2 and 65.8%, respectively, at a styrene conversion of 25.8% over the 7 mol% Ti-SBA-15 catalyst. Beyond this titanium loading, anatase is deposited on the framework and catalytic activity degrades. The performance of the new catalyst is also shown to be superior to conventional materials produced by incipient wetness impregnation where Ti resides on the surface of SBA-15, giving a styrene conversion of 11.9% under identical reaction conditions.     

High Catalytic Performance of Mesoporous Dual Brønsted Acidic Ternary Poly (Ionic Liquids) for Friedel‐Crafts Alkylation

A newfangled cross‐linked dual Brønsted acidic ternary mesoporous poly (ionic liquids)(MPILs) with mesoporous structure was successfully synthesized with divinylbenzene as cross linker, 1‐vinyl‐3‐butyl imidazole bromide and sodium p‐styrene sulfonate as functional group through an ordinary post‐modification method and anion exchange process. A sponge‐like mesoporous tunnel structure was observed and the obtained P (BVS‐SO₃H)‐SO₃CF₃ sample appeared a relatively high thermal stability, a large surface area (up to 286.8 m²/g) and great pore volume (0.73 cm³/g). The abundant dual acidic group of sulfonic acid and trifluoromethanesulfonic acid of the composite in the polymer framework impart Brønsted acidity. For the sake of demonstrating our claims, the sample has been used as a novel solid acid catalyst for the reaction of alkylation of o‐xylene with styrene to 1‐diphenylethane (PXE). Under optimal reaction conditions (reaction under 120 °C for 3 hr, catalyst amount was 0.5 wt% of the reaction system, and the mass ratio of o‐xylene/styrene was 7.5:1, a 100% conversion of styrene and 93.7% PXE yield was acquired. After four times recycle, the yield remains 53.3%. Comparing with the commercial liquid acid catalyst, it processing a higher catalytic property and recyclability. Moreover, this fresh dual acidic heterogeneous catalyst owning a promising future applied in other acidic catalytic reactions and provide a new method to modify catalyst.     

Heterogenization of [Ti(η-C5HMe4)Cl3] on to MCM-41 and organomodified MCM-41 to form epoxidation catalyst

This paper describes the heterogenization of a tetramethylmonocyclopentadienyl titanium (IV) trichloride complex, [Ti(η⁵-C₅HMe₄)Cl₃] onto mesoporous MCM-41. Its immobilization has been performed via a straightforward grafting process of the organometallic precursor in the pores of an MCM-41 host material and by reaction with previously organomodified MCM-41 material with a hydroxyl triazine based compound. Applying all-silica MCM-41 hosts, stable and heterogeneous liquid-phase epoxidation catalysts are obtained. Powder X-ray diffraction and nitrogen adsorption-desorption analysis indicated that the structural integrity of the support has been preserved during the titanium complex immobilization. These materials have been also extensively characterized using diffuse reflectance UV-vis, ¹³C and ²⁸Si MAS NMR and FT-IR spectroscopy. With these techniques the strong adsorption of the intact catalytic complex within an all-silica MCM-41 host is demonstrated. These materials have been tested as catalyst for the epoxidation of aliphatic and aromatic alkenes with TBHP as oxidant exhibiting a significant selectivity toward the epoxide with negligible leaching of titanium species. The conversion values are moderated, being the olefin trend reactivity 1-octene > cyclohexene > styrene.     

Functional mesoporous poly (ionic liquid) derived from P123: From synthesis to catalysis and alkylation of styrene and o‐xylene

A novel strategy was proposed for the fabrication of high‐performance acidic mesoporous poly ionic liquids catalyst. In this work, mesoporous poly ionic liquids (MPILs) were synthesized with P123 (PEO₂₀PPO₇₀PEO₂₀) served as pore‐forming agent. Then, MPILs were treated with PW^3? anion exchange, thereby fabricating PW/MPIL‐S(x). MPIL and PW/MPIL‐S(x) were characterized by scanning electron microscope (SEM), transmission electron microscopy (TEM), Thermogravimetric analysis (TA), N₂ adsorption–desorption and Fourier transform infrared (FT‐IR) spectra and X‐ray photoelectron spectroscopy (XPS) spectra. The effect of solvent and concentration of P123 on the morphology and mesoporous structure of MPILs were investigated systematically. And the results show that MPILs were featured with mesoporous channel structure, high surface area (up to 737 m²/g) and large pore volumes (1.16 cm³/g), which benefit heterogeneous phase reaction (such as, alkylation of styrene with o‐xylene). In the alkylation reaction, under optimal reaction conditions, the catalyst PW/MPIL‐THF (4.0 g) shows high conversion of styrene (100%) and PXE yield (96.21%), demonstrating the excellent catalytic activities. Furthermore, PW/MPIL‐S(x) are easy to be separated from the catalytic system by filtration and show no obvious decrease in catalytic activity after 6 cycle runs. The obtained PW/MPIL‐S(x) catalyst exhibit high thermal and mechanical stability as well, indicating extensive application in high temperature acidic catalysis. This work might open up a new method for the synthesizing of porous polymer catalysts in the future.     

N,B, Si-tridoped mesoporous TiO<Subscript>2</Subscript> with high surface area and excellent visible-light photocatalytic activity

N, B, Si-tridoped mesoporous TiO₂, together with N-doped, N, B-codoped and N, Si-codoped TiO₂, was prepared by a modified sol–gel method. The samples were characterized by wide-angle X-ray diffraction (WAXRD), N₂ adsorption–desorption, transmission electron microscopy (TEM), Fourier transform infrared (FT-IR) spectroscopy, UV–visible adsorbance spectra (UV–vis) and X-ray photoelectron spectra (XPS). The N, B, Si-tridoped mesoporous TiO₂ showed small crystallite size, large specific surface area (350 m²/g), uniform pore distribution (3.2 nm) and strong absorption in the visible light region. The photocatalytic activities of the samples were evaluated by the photodegradation of 2,4-dichlorophenol (2,4-DCP) aqueous solution. The N, B, Si-tridoping sample exhibited much higher photocatalytic activity compared with other synthesized photocatalysts. The high activity could be attributed to the strong absorption in the visible light region, large specific surface area, small crystallite size, large amount of surface hydroxyl groups, and mesoporosity.     

Converting red mud wastes into mesoporous ZSM-5 decorated with TiO2 as an eco-friendly and efficient adsorbent-photocatalyst for dyes removal

Red mud wastes have been converted into mesoporous zeolite socony mobile-5 (ZSM-5) followed by deposited titanium dioxide (TiO₂) nanoparticles to generate synergy adsorption-photodegradation for removal of dye removal in waste water. The amount of TiO₂ loading was varied to achieve optimum photocatalytic activity while maintaining the mesoporosity and high surface area of ZSM-5. Sol-gel method facilitated the formation of anatase TiO₂ on the ZSM-5. The fourier transform infrared spectra clarified the formation of Si–O–Ti at 957 cm^?1 by the exchanging the hydrogen ion with titanium ion, which proved by decreasing the absorption band of Si–OH and Si–O interaction at 964 and 944 cm^?1, respectively. Sol-gel method also preserved the mesopore diameter of ZSM-5 at 3.5 nm which allow the diffusion of methylene blue (MB) molecules into the pores. However, the surface area and the pore volume were slightly reduced with increasing the TiO₂ loading. The adsorption performance of samples showed that the increasing in the TiO₂ loading led to the decreasing in the adsorption capacity. All samples showed the suitability towards the pseudo second order kinetic. The Langmuir isotherm was suitable to describe the adsorption mechanism by monolayer adsorption. Mesoporosity of ZSM-5 accelerated the adsorption of dye via the increase of mass transfer in the pore channel which confirmed by the low intercept of intraparticle diffusion model at the first stage. The photocatalytic test showed that 10% TiO₂ loading on the ZSM-5 exhibited the highest methylene blue removal followed by 5% and 20% TiO₂ loading. Optimization on the amount of photocatalyst and the pH of solution indicated the reaction favoured 1 g L^?1 of catalysts and at alkaline pH. 10% TiO₂/ZSM-5 also exhibited high stability and reusability up to four reaction cycles. Photocatalytic performance of 10% TiO₂/ZSM-5 was further investigated on photodegradation of malachite green and rhodamine B organic dyes, which showed the photocatalytic efficiency of 73 and 88%, respectively. Superoxide radical, hydroxyl radical, and photogenerated electron were identified as the main active species for MB photodegradation based on the reduction of degradation rate following the addition scavenger molecules.     

Tuning the wall thickness and pore orientation in mesoporous titania films prepared with low-temperature aging

Porous titania thin films with well-ordered mesostructures are prepared by using Pluronic surfactant P123 as the pore template and aging the films in a high-humidity environment at −6 °C. These structures are stable enough to undergo calcination at 400 °C to generate nanocrystalline TiO₂ walls with retention of mesoporosity. Under the aging conditions used, the films have well-ordered mesostructures even with a molar ratio of P123 to titanium (R) as small as 0.006. Because the P123 micelle diameter remains constant across a range of compositions, the pore diameter also remains fixed but the wall thickness of the titania thin films increases as the P123 concentration decreases without decreasing the long-range order of the products. Furthermore, mesoporous titania thin films with hexagonal close-packed channels oriented perpendicular to the substrate can be obtained R values of 0.008–0.012 by sandwiching the as-prepared films between glass slides modified with crosslinked P123. Analysis of the mesophases obtained here indicates that a transition from films containing significant 2D hexagonal channels to 3D hexagonal structure occurs below P123/Ti = 0.008. This does not match the expected volume fraction for this transition based on the mesophases behavior of aqueous P123 at room temperature, suggesting that a more detailed model would be needed to predict mesostructure in titania films aged below the freezing point of water.     

The effects of the crystallization rate of the mesoporous TiO2 on the stability of the mesoporous structure after reflux

A simple synthetic method was employed to prepare mesoporous titania with anatase crystalline walls and high photocatalytic activity. The properties and structures of mesoporous titania were characterized by means of low angle and wide angle X-ray diffraction (XRD), Fourier transform (FT)-IR spectra, transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), and N₂ adsorption–desorption. The characteristic results clearly show that crystallization rate of the mesoporous titania affects the stability of the mesoporous structure after reflux, and that the anatase crystal in the mesoporous wall of mesoporous titania can stabilize the mesoporous structure. The photocatalytic activity of titania powder was evaluated from an analysis of the photodegradation of methyl orange under UV irradiation. The results indicate that the titania powder with mesoporous structure shows the highest photocatalytic activity.     

Improvement of the Visible‐Light Photocatalytic Performance of TiO2 by Carbon Mesostructures

An improvement in the photodegradation performance for dyes due to interaction between carbon and titania in a self‐assembled mesoporous C? TiO₂ composite catalyst, even for the difficult degradation of azo dyes, is reported herein. The dye removal process involves adsorption of the dye from water by the mesoporous carbon–titania, followed by photodegradation on the separated dye‐loaded solid. Such adsorption–catalysis cycles can be carried out more than 80 times without discernible loss of photocatalytic activity or the anatase content of the composite. In each run, about 120 mg dye per g catalyst can be degraded. The mesoporous carbon–titania catalyst also exhibits a high capacity for converting methyl orange in aqueous solution under visible light. Characterization by XRD, TEM, and N₂ sorption techniques has revealed that the self‐assembled composite catalyst has an ordered mesostructure, uniform mesopores (4.3 nm), a large pore volume (0.30 cm³ g^?1), and a high surface area (348 m² g^?1). The pore walls are composed of amorphous carbon and anatase nanoparticles of size 4.2 nm, which are well dispersed and confined. X‐ray photoelectron spectroscopy (XPS), surface photovoltage spectroscopy (SPS), and UV/Vis absorption results indicate doping of carbon into the anatase lattice and a change in the bandgap of the semiconductor. The synergistic improvement in the composite catalyst can be attributed to the following features: (1) carbon doping of the anatase lattice modifies its bandgap and enhances its activity under visible light; (2) confinement within carbon pore walls prevents aggregation of tiny anatase nanoparticles, improving their activity and stability; (3) the mesopores provide a confined space for photocatalysis; and (4) the strong adsorption ability of porous carbon for organic substances ensures that large quantities can be processed and inhibits further diffusion of the adsorbed organic substances, thereby enhancing the mineralization on anatase.     

Preparation and characterization of nanocomposites in system as: SnO<Subscript>2</Subscript>–xTiO<Subscript>2</Subscript> (where <Emphasis Type="Italic">x</Emphasis> = 25, 50 and 75 mol%)

Nanocomposite samples containing various molar compositions of tin and titanium oxides were synthesized by a sol–gel method using octadecylamine as controlling template agent. The structural and the crystalline features of the samples were investigated with Fourier Transformer Infra-red, X-ray diffraction, Transmission electron microscope (TEM) where the surface area was estimated by BET analysis. The crystalline parameters and the particle size were estimated by Rietveld quantitative phase analysis. It is interesting to mention that a reduction in the lattice parameters was detected upon introduction of various molar compositions of titanium oxide revealing that a part of titania is incorporated into the SnO₂ lattice forming Ti_1−xSn_xO₂ solid solution. The quantitative analysis claims that part of titanium oxide is incorporated substitutionally in the crystal lattice of SnO₂, forming a solid solution and other parts are either segregated as separate rutile titania phase or dispersed as amorphous phase on the grain boundary of SnO₂. The results show a remarkable reduction in particle size from 42 to 5 nm and increasing in the specific surface area up to 176 m²/g upon introduction of various content of titania implying the role of titania particles in preventing SnO₂ crystallites from further growing up during the progress of calcination. TEM images show that pure tin oxide particles arranged in large aggregation in wormhole like structure, while the existence of titanium oxide are successfully creates spherical nanoparticles system organized in a definite structure. The optical absorbance spectra indicate a red shift and band gap narrowing upon introduction of titania which increase with increasing in titania contents.     

Fabrication of synthetic opals composed of mesoporous SnO2 spheres with an anodization-assisted double template process

Synthetic opals composed of mesoporous SnO₂ spheres were successfully fabricated from anodization of Sn opals, double templated from polystyrene opals. The mesoporous SnO₂ spheres were 440 nm in diameter containing mesopores of 20–40 nm. The resultant mesoporous SnO₂ opals possessed a high specific surface area of 196 m²/g and a grain size of 12 nm as estimated from XRD patterns. Such a hierarchical structure of SnO₂ is a promising candidate for applications in gas sensors, catalysts, and electrode materials since the regularity of the sub-micron opal structure eases transfers of relevant chemical species within the structure while the mesoporosity of the constituent SnO₂ spheres offers sufficient functioning surfaces for targeted applications.     

Aqueous Long-Term Solubility of Titania Nanoparticles and Titanium(IV) Hydrolysis in a Sodium Chloride System Studied by Adsorptive Stripping Voltammetry

The solubility of industrially produced titanium dioxide nanoparticles has been studied in aqueous sodium chloride media in the pH range 1 to 13 at 25 °C by using adsorptive stripping voltammetry (AdSV). Kinetic dissolution curves have been obtained as well as long-term solubilities that provide an approximation of the equilibrium solubilities. The titania nanoparticles used in the dissolution experiments have been characterized by nitrogen sorption measurements, XRD and colloid titration. The equilibrium solubilities and titanium(IV) speciation and their dependences on pH have been modelled by assuming the formation of the mononuclear titanium hydroxo complexes [Ti(OH) _n ]⁽⁴⁻ⁿ⁾⁺ (n=2 to 5) to be the only titanium species present. The solubility product of titanium dioxide and equilibrium constants for titanium(IV) hydrolysis, calculated from the AdSV solubility data, are presented.     

Effect of calcination atmosphere on the structure and photocatalytic properties of titania mesoporous powder

In the work presented here, mesoporous titania (MTO) powders are synthesised by the sol?Cgel method using amphiphilic triblock copolymer as a template in two different calcination atmospheres, N₂ and air. Various techniques such as sequential thermal analysis (STA), small-angle X-ray diffraction (SAXRD), wide-angle X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), ultraviolet (UV)?Cvisible spectroscopy, high-resolution transmission electron microscopy (HRTEM) and N₂-adsorption/desorption analysis were utilised to study the prepared samples. Furthermore, the photocatalytic activities of the prepared samples were evaluated from the photo-degradation analysis of methylene blue (MB). For the sample calcined at N₂, the formation of an ordered mesostructure with a high specific surface area (172?m²?g^?1), mesoporosity (48%) and enhanced photocatalytic activity were obtained compared to that of the sample calcined in air. The observed increased MB degradation for the latter is mainly attributed to the formation of higher specific surface area and mesoporosity. The availability of highly ordered open-pore channels could provide increased contacts between reactants in the solution and the active sites on the surface of titania mesoporous particles. Considering the photoactivities of the samples, it is revealed that the photocatalytic activity is enhanced, together with an increase in the surface defects in N₂ atmosphere.     

Synthesis and characterization of Cr-MSU-1 and its catalytic application for oxidation of styrene

Chromium-containing mesoporous silica material Cr-MSU-1 was synthesized using lauryl alcohol-polyoxyethylene (23) ether as templating agent under the neutral pH condition by two-step method. The sample was characterized by XRD, TEM, FT-IR, UV-Vis, ESR, ICP-AES and N₂ adsorption. Its catalytic performance for oxidation of styrene was studied. Effects of the solvent used, the styrene/H₂O₂ mole ratio and the reaction temperature and time on the oxidation of styrene over the Cr-MSU-1 catalyst were examined. The results indicate that Cr ions have been successfully incorporated into the framework of MSU-1 and the Cr-MSU-1 material has a uniform worm-like holes mesoporous structure. After Cr-MSU-1 is calcined, most of Cr³⁺ is oxidized to Cr⁵⁺ and Cr⁶⁺ in tetrahedral coordination and no extra-framework Cr₂O₃ is formed. The Cr-MSU-1 catalyst is highly active for the selective oxidation of styrene and the main reaction products over Cr-MSU-1 are benzaldehyde and phenylacetaldehyde. Its catalytic performance remains stable within five repeated runs and no leaching is noticed for this chromium-based catalyst.     

Synthesis,characterization and catalytic properties of heterogeneous iron(III) tetradentate Schiff base complexes for the aerobic epoxidation of styrene

A series of hybrid mesoporous SBA-15 materials containing four iron(III) Schiff base complexes of the type [FeL ^x (NO₃)] (x = 4–7, L = N,N′-bis(salicylidene)ethylenediamine, N,N′-bis(salicylidene)diethylenetriamine, N,N′-bis(salicylidene)o-phenylenediamine, N,N′-bis(3-nitro-salicylidene)ethylenediamine) was synthesized by a post-grafting route. The XRD, N₂ adsorption/desorption and TEM measurements confirmed the structural integrity of the mesoporous hosts, and the spectroscopic characterization techniques (FT-IR, UV–vis spectroscopy, ¹H NMR) confirmed the ligands and the successful anchoring of iron(III) Schiff base complexes over the modified mesoporous support. Quantification of the supported ligand and metal was carried out by TG/DSC and ICP-AES techniques. The catalyst FeL⁷-SBA resulting from N,N′-bis(3-nitro-salicylidene)ethylenediamine) ligand was considerably active for the aerobic epoxidation of styrene, in which the highest conversion of styrene reached 83.6%, and the selectivity to styrene oxide was 83.0%. Moreover, it was also found that the catalytic activity increases with the decrease in the electron-donating ability of the Schiff bases, and the selectivity varies according to the types of substituents in the ligands.     

Preparation of ordered mesoporous TiO2 thin film and its application in methanol catalytic combustion

Ordered mesoporous titania thin films were synthesized by evaporation induced self‐assembly process in the presence of Pluronic block copolymers P123 (EO₂₀‐PO₇₀‐EO₂₀). The influence of several experimental parameters, including aging humidity, aging temperature, substrate properties and methods for organic templates removal, on the mesostructure of titania thin films was investigated in details. The mesoporous titania thin film supported Pt catalyst was prepared, and its methanol catalytic combustion performance was studied. The results showed that mesoporous titania thin film is an active support for catalyst. Mesoporous titania thin film supported platinum catalysts yields 70% methanol conversion at room temperature and 100% conversion at 100 °C. Copyright © 2013 John Wiley & Sons, Ltd.     

Facile preparation of transparent monolithic titania gels utilizing a chelating ligand and mineral salts

Highly homogeneous transparent titania gels have been successfully prepared from titanium alkoxide by a sol–gel method utilizing chelating agent, ethyl acetylacetate (EtAcAc), in the presence of strong acid anions. Only catalytic amount of a strong acid anion suppress the rapid hydrolysis of titanium alkoxide by blocking the nucleophilic attack of HO⁻ and H₂O, and the resultant moderate sol–gel reactions thus afford homogeneous gelation, leading to transparent monolithic titania gels. Gelation time can be widely controlled by changing amounts of water, chelating agent and salt. The ability of salts to suppress the too abrupt sol–gel reactions is strongly dependent on the electronegativity of anions and valence of cations. With employing NH₄NO₃ as a suppressing electrolyte, the obtained titania gels can be converted to pure TiO₂ by simple washing and heat-treatment, and transformations to anatase and rutile structures were found to start at 400 and 600 °C, respectively.     

N‐heterocyclic carbene–palladium(II) complex supported on magnetic mesoporous silica for Heck cross‐coupling reaction

Magnetic mesoporous silica was prepared via embedding magnetite nanoparticles between channels of mesoporous silica (SBA‐15). The prepared composite (Fe₃O₄@SiO₂‐SBA) was then reacted with 3‐chloropropyltriethoxysilane, sodium imidazolide and 2‐bromopyridine to give 3‐(pyridin‐2‐yl)‐1H‐imidazol‐3‐iumpropyl‐functionalized Fe₃O₄@SiO₂‐SBA as a supported pincer ligand for Pd(II). The functionalized magnetic mesoporous silica was further reacted with [PdCl₂(SMe₂)₂] to produce a supported N‐heterocyclic carbene–Pd(II) complex. The obtained catalyst was characterized using Fourier transform infrared spectroscopy, scanning electron microscopy, energy‐dispersive X‐ray analysis, vibrating sample magnetometry, Brunauer–Emmett–Teller surface area measurement and X‐ray diffraction. The amount of the loaded complex was 80.3 mg g^?1, as calculated through thermogravimetric analysis. The formation of the ordered mesoporous structure of SBA‐15 was confirmed using low‐angle X‐ray diffraction and transmission electron microscopy. Also, X‐ray photoelectron spectroscopy confirmed the presence of the Pd(II) complex on the magnetic support. The prepared magnetic catalyst was then effectively used in the coupling reaction of olefins with aryl halides, i.e. the Heck reaction, in the presence of a base. The reaction parameters, such as solvent, base, temperature, amount of catalyst and reactant ratio, were optimized by choosing the coupling reaction of 1‐bromonaphthalene and styrene as a model Heck reaction. N‐Methylpyrrolidone as solvent, 0.25 mol% catalyst, K₂CO₃ as base, reaction temperature of 120°C and ultrasonication of the catalyst for 10 min before use provided the best conditions for the Heck cross‐coupling reaction. The best results were observed for aryl bromides and iodides while aryl chlorides were found to be less reactive. The catalyst exhibited noticeable stability and reusability.     

Synthesis of highly ordered mesoporous CeO<Subscript>2</Subscript> and low temperature CO oxidation over Pd/mesoporous CeO<Subscript>2</Subscript>

Highly ordered mesoporous cerium dioxide (meso-CeO₂) was successfully synthesized using a facile solvent-free infiltration method from a mesoporous silica template, KIT-6. The meso-CeO₂ material, thus obtained, exhibited well-defined mesostructure and high surface area (153 m² g⁻¹). The physicochemical properties of meso-CeO₂ material and Pd-supported on meso-CeO₂ (Pd/meso-CeO₂) were characterized by electron microscopy, X-ray diffraction, N₂ adsorption–desorption, and temperature-programmed experiments. The Pd/meso-CeO₂ catalyst exhibited excellent catalytic activity for CO oxidation compared with those of other Pd/CeO₂ catalysts which were prepared using nanocrystalline CeO₂ and bulk-CeO₂ as the supports. Moreover, a hydrogen pretreatment of the Pd/meso-CeO₂ catalyst resulted in a remarkable increase of catalytic activity (T ₁₀₀ = 52 °C).     

Effective synthesis of nanoscale anatase TiO2 single crystals using activated carbon template to enhance the photodegradation of crystal violet

Nanoscale anatase TiO₂ single crystals were successfully synthesized using three kinds of activated carbon (AC) templates through a simple sol–gel method. The optimal photocatalyst (T‐WOAC) was obtained using wood‐based AC template. X‐ray diffraction, transmission electron microscopy and Brunauer–Emmett–Teller analyses revealed that T‐WOAC possessed a small crystallite size of 8.7 nm and a clear mesoporous structure. The photocatalytic properties of samples were then evaluated through photodegradation of crystal violet (CV). Results implied that the photocatalysts prepared using the AC templates exhibited superior photocatalytic activity to that of the original TiO₂. This enhancement may be due to the small crystallite size, large specific surface area and pore volume of the catalysts prepared with ACs. T‐WOAC showed high photocatalytic activity, CV degradation of 99.01% after 120 min of irradiation and k = 0.03914 min^?1, which is 3.9 times higher than that of the original TiO₂ (k = 0.00994 min^?1). This result can be mainly attributed to the application of WOAC with moderate specific surface area and pore volume to produce T‐WOAC. Alkaline conditions benefitted the photodegradation of CV over photocatalysts. This work proposes a possible degradation mechanism of CV and indicates that the fabricated photocatalysts can be used to effectively remove CV from aqueous solutions.