Effect of ceria loading on the carbon formation during low temperature methane steam reforming over a Ni/CeO2/ZrO2 catalyst

The characterization and catalytic activity of a Ni/CeO₂/ZrO₂ catalyst for methane steam reforming at 600°C were investigated. The addition of ceria increased the surface area and basicity of the catalysts. The redox reaction capability of the ceria increased the hydrogen yield and carbon monoxide selectivity, and inhibited carbon formation.     

Structural characterization and photocatalytic activity of hollow binary ZrO2/TiO2 oxide fibers

The formation of hollow binary ZrO₂/TiO₂ oxide fibers using mixed precursor solutions was achieved by activated carbon fibers templating technique combined with solvothermal process. The samples were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), N₂ adsorption, X-ray photoelectron spectroscopy (XPS), UV-vis, and infrared (IR) spectroscopy. The binary oxide system shows the anatase-type TiO₂ and tetragonal phase of ZrO₂, and the introduction of ZrO₂ notably inhibits the growth of TiO₂ nanocrystallites. Although calcined at 575 °C, all hollow ZrO₂/TiO₂ fibers exhibit higher surface areas (>113 m²/g) than pure TiO₂ hollow fibers. The Pyridine adsorption on ZrO₂/TiO₂ sample indicates the presence of stronger surface acid sites. Such properties bring about that the binary oxide system possesses higher efficiency and durable activity stability for photodegradation of gaseous ethylene and trichloromethane than P25 TiO₂. In addition, the macroscopic felt form for the resulting materials is more beneficial for practical applications than traditional catalysts forms.     

TiO2 nanoparticles incorporated with CuInS2 clusters: preparation and photocatalytic activity for degradation of 4-nitrophenol

TiO₂ nanoparticles incorporated with CuInS₂ clusters were prepared in a solvothermal process and characterized with X-ray diffraction (XRD), transmission electron microscopy (TEM), and energy-dispersion X-ray analysis (EDX). Compared with pure TiO₂ nanoparticles, the TiO₂ nanoparticles incorporated with CuInS₂ clusters display higher photocatalytic activity with 99.9% of degradation ratio of 4-nitrophenol after 2 h irradiation. In order to investigate the effect of the CuInS₂ clusters on the photocatalytic activity of TiO₂ nanoparticles, diffuse reflectance UV–Vis spectra (DRS), photoluminescence (PL) spectra, and photocurrent action spectra were measured. The results indicate that the enhanced photocatalytic activity is probably due to the interface between TiO₂ and CuInS₂ as a trap of the photogenerated electrons to decrease the recombination of electrons and holes.     

Preparation and photocatalytic activity of ZnO/TiO2/SnO2 mixture

ZnO/TiO₂/SnO₂ mixture was prepared by mixing its component solid oxides ZnO, TiO₂ and SnO₂ in the molar ratio of 4?1?1, followed by calcining the solid mixture at 200-1300 °C. The products and solid-state reaction process during the calcinations were characterized with powder X-ray diffraction (XRD), thermogravimetric and differential thermal analysis (TG-DTA), UV-Vis diffuse reflectance spectroscopy (UV-Vis DRS) and Brunauer-Emmett-Teller measurement of specific surface area. Neither solid-state reaction nor change of crystal phase composition took place among the ZnO, TiO₂ and SnO₂ powders on the calcinations up to 600 °C. However, formation of the inverse spinel Zn₂TiO₄ and Zn₂SnO₄ was detected at 700-900 and 1100-1200 °C, respectively. Further increase of the calcination temperature enabled the mixture to form a single-phase solid solution Zn₂Ti_0.5Sn_0.5O₄ with an inverse spinel structure in the space group of . The ZnO/TiO₂/SnO₂ mixture was photocatalytically active for the degradation of methyl orange in water; its photocatalytic mass activity was 16.4 times that of SnO₂, 2.0 times that of TiO₂, and 0.92 times that of ZnO after calcination at 500 °C for 2 h. But, the mass activity of the mixture decreased with increasing the calcination temperature at above 700 °C because of the formation of the photoinactive Zn₂TiO₄, Zn₂SnO₄ and Zn₂Ti_0.5Sn_0.5O₄. The sample became completely inert for the photocatalysis after prolonged calcination at 1300 °C (42 h), since all of the active component oxides were reacted to form the solid solution Zn₂Ti_0.5Sn_0.5O₄ with no photocatalytic activity.     

甲烷在Ni/TiO2催化剂表面的活化

考察了Ni/TiO2催化剂甲烷部分氧化和二氧化碳重整制合成气的反应活性,实验表明,以TiO2为载体的镍系催化剂对于甲烷部分氧化制合成气反应具有较好的活性,尤其对H2的选择性较高,对二氧化碳重整制合成气反应具有较好的低温反应活性.采用脉冲-质谱在线分析等技术,在无气相氧条件下向Ni/TiO2催化剂脉冲CH4,发现甲烷在催化剂表面的活化（转化）及其氧化产物的选择性与金属催化剂表面氧的浓度密切相关.CH4与Ni/TiO2催化剂作用过程中存在明显的氢溢流和氧溢流现象,可能是这种溢流效应使得Ni/TiO2催化剂具有良好的反应活性和抗积碳性能.     

CO2 reforming of methane over zirconia-supported nickel catalysts, I. Catalytic specificity

CO₂ reforming of methane is performed over zirconia-supported nickel catalysts. The catalysts show high activity toward CH₄ and CO₂ conversions. Over the high Ni loading catalyst, long-term performances without significant deactivations have been achieved at 1023 K for 30 h and 1123 K for 20 h, respectively. The effects of reduction and calcination temperatures on the catalytic activities are also examined.     

ZnFe2O4/Ag/TiO2复合材料的制备及其光催化性能

以硝酸银、钛酸四丁酯、无水氯化锌、六水氯化铁为原料,采用溶胶-凝胶法与溶剂热相结合的方法制备了ZnFe₂O₄/Ag/TiO₂复合材料,通过扫描电子显微镜、能谱分析仪、X射线粉末衍射仪、X射线光电子能谱仪、振动样品磁强计、紫外可见分光光度计对样品进行表征及测试。结果表明： ZnFe₂O₄/Ag/TiO₂-10具有最佳的光催化效果,在紫外和可见光下对染料的降解率都能达到90%以上,具有优异的紫外可见光光催化活性。ZnFe₂O₄/Ag/TiO₂具有独特的磁性,能在外部磁场作用下进行回收利用,这使其在实际应用中成为可能。通过磁分离技术重复回收利用5次后仍然保持优良的光催化性能,说明ZnFe₂O₄/Ag/TiO₂-10具有优异的磁性及较高的光催化循环稳定性。     

ZnFe2O4/Ag/TiO2复合材料的制备及其光催化性能

以硝酸银、钛酸四丁酯、无水氯化锌、六水氯化铁为原料,采用溶胶-凝胶法与溶剂热相结合的方法制备了ZnFe₂O₄/Ag/TiO₂复合材料,通过扫描电子显微镜、能谱分析仪、X射线粉末衍射仪、X射线光电子能谱仪、振动样品磁强计、紫外可见分光光度计对样品进行表征及测试。结果表明：ZnFe₂O₄/Ag/TiO₂-10具有最佳的光催化效果,在紫外和可见光下对染料的降解率都能达到90%以上,具有优异的紫外可见光光催化活性。ZnFe₂O₄/Ag/TiO₂具有独特的磁性,能在外部磁场作用下进行回收利用,这使其在实际应用中成为可能。通过磁分离技术重复回收利用5次后仍然保持优良的光催化性能,说明ZnFe₂O₄/Ag/TiO₂-10具有优异的磁性及较高的光催化循环稳定性。     

The preparation and characterization of La doped TiO2 nanoparticles and their photocatalytic activity

In this paper, pure and La doped TiO₂ nanoparticles with different La content were prepared by a sol-gel process using Ti (OC₄H₉)₄ as raw material, and also were characterized by XRD, TG-DTA, TEM, XPS, DRS and Photoluminescence (PL) spectra. We mainly investigated the effects of calcining temperature and La content on the properties and the photocatalytic activity for degrading phenol of as-prepared TiO₂ samples, and also discussed the relationships between PL spectra and photocatalytic activity as well as the mechanisms of La doping on TiO₂ phase transformation. The results showed that La³⁺ did not enter into the crystal lattices of TiO₂ and was uniformly dispersed onto TiO₂ as the form of La₂O₃ particles with small size, which possibly made La dopant have a great inhibition on TiO₂ phase transformation; La dopant did not give rise to a new PL signal, but it could improve the intensity of PL spectra with a appropriate La content, which was possibly attributed to the increase in the content of surface oxygen vacancies and defects after doping La; La doped TiO₂ nanoparticles calcined at 600°C exhibited higher photocatalytic activity, indicating that 600°C was an appropriate calcination temperature. The order of photocatalytic activity of La doped TiO₂ samples with different La content was as following: 1>1.5>3>0.5>5>0 mol%, which was the same as the order of their PL intensity, namely, the stronger the PL intensity, the higher the photocatalytic activity, demonstrating that there were certain relationships between PL spectra and photocatalytic activity. This could be explained by the points that PL spectra mainly resulted from surface oxygen vacancies and defects during the process of PL, while surface oxygen vacancies and defects could be favorable in capturing the photoinduced electrons during the process of photocatalytic reactions.     

Preparation and photocatalytic activity of Sb2S3/Bi2S3 doped TiO2 from complex precursor via gel-hydrothermal treatment

Sb₂S₃/Bi₂S₃ doped TiO₂ were prepared with the coordination compounds [M(S₂CNEt)₃] (M=Sb, Bi; S₂CNEt=pyrrolidinedithiocarbamate) as precursors via gel-hydrothermal techniques. The doped TiO₂ were characterized by XRD, SEM, XPS and UV-vis diffuse reflectance means. The photocatalyst based on doped TiO₂ for photodecolorization of 4-nitrophenol (4-NP) was examined. The optimal Bi₂S₃/Sb₂S₃ content, pH and different doped techniques have been investigated. Photocatalytic tests reveal that M₂S₃ doped TiO₂ via the gel-hydrothermal route performs better photocatalytic activity for photodegradation reaction of 4-nitrophenol (4-NP).     

Synthesis of nanosized TiO2/SiO2 catalysts by the ultrasonic microemulsion method and their photocatalytic activity

Nanosized TiO₂/SiO₂ catalysts prepared by hydrolysis of titanium n-butoxide in microemulsion showed enhanced photocatalytic activity. In the presence of catalyst ME-2 and after 90 min irradiation by UV light, methylene blue was completely converted evidenced by the absence of its absorption band in the UV-Vis spectra. This catalyst demonstrated much better degradation ability than P-25 and naked TiO₂.     

Surface modification of thermoplastics by atomic layer deposition of Al2O3 and TiO2 thin films

Al₂O₃ and TiO₂ thin films were deposited by atomic layer deposition at 80-250 °C on various polymeric substrates such as polymethylmethacrylate (PMMA), polyetheretherketone (PEEK), polytetrafluoroethylene (PTFE) and ethylenetetrafluoroethylene (ETFE). The films were studied with FESEM, EDX, XRD, contact angle measurements and adhesion tests. The film growth rates on the thermoplastics were close to the corresponding growth rates on Si substrates. The adhesion of the films was good on PEEK and poor on PTFE. All coated surfaces showed lower water contact angles than the uncoated thermoplastics. Furthermore, the water contact angles on all TiO₂-coated surfaces decreased upon UV illumination, most efficiently with crystalline TiO₂ coatings.     

The release of TiO2 and SiO2 nanoparticles from nanocomposites

There is a growing interest in the development of nanocomposites consisting of organic polymers and TiO₂ or amorphous SiO₂ nanoparticles. These nanoparticles may be released from nanocomposites. There is evidence that amorphous SiO₂ and TiO₂ nanoparticles can be hazardous. Thus, in the design of nanocomposites with such nanoparticles, hazard reduction extending to the full nanocomposite life cycle would seem a matter to consider. Options for hazard reduction include: changes of nanoparticle surface, structure or composition, better fixation of nanoparticles in nanocomposites, including persistent suppression of oxidative damage to polymers by nanoparticles, and design changes leading to the release of relatively large particles.     

Preparation and characterization of CoFe2O4/TiO2 magnetic composite films

CoFe₂O₄/TiO₂ magnetic composite films were prepared using the sol-gel method with tetrabutyltitanate and metallic chlorates as starting materials. The effects of heat treatment temperatures on microstructures and on magnetic properties were studied. The microstructure and properties of the samples at different heat treatment temperatures were characterized by X-ray diffraction, Raman spectrum, scanning electron microscopy, polarized microscopy and vibrating sample magnetometry. The results show that crystals of different substances grow up independently. Cobalt ferrite is evenly embedded into the titanium dioxide matrix in the prepared composite films. The magnetism of the composite films is enhanced with an increase of the heat temperature. Supported by the National Natural Science Foundation of China (Grant Nos. 50632030 and 10474077), and the Natural Science Foundation of Shaanxi Province (Grant No. 2006E135)     

Catalytic oxidation of no to NO2 over Cr/TiO2 and Cu/TiO2 under oxidizing atmosphere

The catalytic activity of Cr/TiO₂ and Cu/TiO₂ for the oxidation of NO under an oxidizing atmosphere has been examined. Both catalysts had excellent ability for the oxidation of NO to NO₂ in the temperature range of 350–400°C.     

TiO2/Cu2O/Pt复合空心微球的制备及其光催化性能

以锐钛矿相TiO₂溶胶为基底,采用沉淀法和液相沉积法制备了TiO₂/Cu₂O/Pt复合空心微球,通过改变n_Ti⁴⁺∶ n_Cu²⁺和H₂PtCl₆·6 H₂O溶液的加入量对TiO₂的形貌和结构进行调控,采用不同的方法对不同样品的物相及结构、微观形貌和光学性能进行了对比分析。分析结果表明,复合材料中Pt与Cu₂O的引入产生协同效应,不仅在一定程度上阻止了电子-空穴的复合,还降低了禁带宽度,在可见光区域光吸收明显增强。与TiO₂、Cu₂O和TiO₂/Cu₂O光催化剂相比较,TiO₂/Cu₂O/Pt降解有机污染物的能力显著增强,首次光照120 min可降解93%的甲基橙(MO)溶液,4次循环后降解率为71%,具有良好的光催化稳定性能。     

TiO2/Cu2O/Pt复合空心微球的制备及其光催化性能

以锐钛矿相TiO₂溶胶为基底,采用沉淀法和液相沉积法制备了TiO₂/Cu₂O/Pt复合空心微球,通过改变n₍Ti⁴⁺)∶n_Cu2+和H₂Pt Cl₆·6H₂O溶液的加入量对TiO₂的形貌和结构进行调控,采用不同的方法对不同样品的物相及结构、微观形貌和光学性能进行了对比分析。分析结果表明,复合材料中Pt与Cu₂O的引入产生协同效应,不仅在一定程度上阻止了电子-空穴的复合,还降低了禁带宽度,在可见光区域光吸收明显增强。与TiO₂、Cu₂O和TiO₂/Cu₂O光催化剂相比较,TiO₂/Cu₂O/Pt降解有机污染物的能力显著增强,首次光照120 min可降解93%的甲基橙(MO)溶液,4次循环后降解率为71%,具有良好的光催化...     

Synthesis of bimodal porous structured TiO2 microsphere with high photocatalytic activity for water treatment

In this work bimodal structured titanium dioxide (TiO₂) microsphere has been prepared from commercial TiO₂ powder and nano-sized titania gel via sol–gel spray-coating technique. Crystallization and transformation behavior of titania gel were investigated. The results revealed that the crystallization and transformation of anatase particles were substantially affected by the concentration of solvent and calcination temperature. Anatase crystallite size of 10 nm was obtained at mole ratio of solvent/precursor 50/1 and calcination temperature of 450 °C. The prepared nano-sized titania gel was embedded within the core (commercial TiO₂, P25) during the spraying process. The prepared TiO₂ microsphere was characterized using X-ray diffractometer (XRD), scanning electron microscope (SEM), field emission electron microscope (FESEM) and micropore analysis. The photocatalytic activity was monitored by following the degradation of phenol with activity benchmarked against commercial P25 (Degussa). The increase of photocatalytic activity of TiO₂ microsphere was attributed to the nano-sized anatase crystallite which has been incorporated into the TiO₂ microsphere.     

Effect of electrolysis conditions on photocatalytic activities of the anodized TiO2 films

Photocatalytic activities of anodized TiO₂ films for decomposition of gaseous acetaldehyde were investigated. The anodized TiO₂ films were fabricated by galvanostatic anodization in a mixed electrolyte composed of H₂SO₄, H₃PO₄, and H₂O₂. Pre-nitridation treatment effectively enhanced the photocatalytic activity of the anodized TiO₂ films. The electrolysis parameters such as anodization time, current density, electrolyte temperature, and electrolyte composition significantly affected the photocatalytic activity of the anodized TiO₂ films. The improvement of photocatalytic activity of the anodized films is attributed to increase in surface areas of the anodized specimens.     

H2 production with low CO selectivity from photocatalytic reforming of glucose on metal/TiO2 catalysts

H₂ with low CO concentration is produced via photocatalytic reforming of glucose (as a representative of biomass component) on metal/TiO₂ catalyst (metals: Pt, Rh, Ru, Ir, Au, Ni, Cu). It is shown that the loaded metals generally enhance the rate of H₂ production, while they depress the CO selectivity. Both H₂ production and CO selectivity are strongly dependent on the kind of deposited metals on TiO₂. For example, Rh/TiO₂ catalyst is found to be most active for H₂ production while with the most extremely low CO concentration from the photocatalytic reforming of glucose. Supported by the National Natural Science Foundation of China (Grant No. 20403018, 20503034), National Basic Research Program of China (Grant No. 2003CB214504), and Knowledge Innovation Program of the Chinese Academy of Sciences (DICP K2006E2)