Synthesis of mesoporous silica-embedded TiO<Subscript>2</Subscript> loaded with Ag nanoparticles for photocatalytic hydrogen evolution from water splitting

Ag loaded mesoporous silica-embedded TiO₂ nanocomposites were successfully synthesized via two different routes, including one-pot solvothermal method and solvothermal-chemical reduction method, both using Titanium (IV) n-butoxide (Ti(OC₄H₉)₄) as a precursor, formic acid as a solvent and reducing agent, silver nitrate as a silver source and tetraethyl silicate (TEOS) as a stabilizer. The transmission electron microscopic (TEM) images showed that silica-embedded anatase TiO₂ sample exhibited approximately rhombic shape and Ag nanoparticles could be embedded into the nanocomposites or deposited on the surface with high dispersion. The N₂ adsorption-desorption isotherms indicated that the silica-embedded anatase TiO₂ had obvious mesoporous structure with a BET specific surface area of 203.5 m²·g^-1. All Ag loaded silica-embedded TiO₂ composites showed a higher photocatalytic H₂-generation activity from water splitting under simulative solar light irradiation than that of TiO₂ products. The maximum H₂ production rate (6.10 mmol·h^-1·g^-1) was obtained over 2% Ag/silica-embedded TiO₂ nanocomposites (2% Ag/MST) prepared by solvothermal-chemical reduction method, which was 20 times that achieved on the silica-embedded TiO₂ sample. The enhanced photocatalytic H₂-evolution activity of Ag loaded mesoporous silica-embedded TiO₂ nanocomposites can be attributed to the multi-function of surface Ag co-catalyst, mesoporous structure, and embedding of silica.     

Structrue and Characteristics of Mesoporous Silica Synthesized in Acid Medium and Its Reaction Mechanism

Structrue and pore characteristics of the mesoporous silica synthesized in acid medium were studied by means of XRD, HRTEM, BET, FT-IR, DSC-TGA, and the reaction mechanism was also investigated deeply. The results show that mesopores in the sample possess hexagonal arrays obviously, whereas the structure of silica matrix is amorphous. The results also show that the acting mode of silica and CTMA^ inside the mesopores was chemical bonding force. The structure of rnesoporous silica was mainly dependent on the aggregational condition of micelle of CTMA^ as well as their liquid- crystallized status. In addition, condensation and dehydration of silicate radicals were accompanied in the process of calcination, which resulted in the mesoporous structure ordered in local range and the pore sizes largening.     

Different Synthesis Methods for Ordered Mesoporous Silicas And Their Characteristics Comparison

1　IntroductionInorganicmesoporousmaterialshaveahighpotentialforapplicationsinthefieldsofcatalysis,adsorption ,sepa rationprocesses,biologymaterials,novelopticalmaterialsetc.Mesoporousmaterialshaverapidlyattractedresearchinterestsinthefieldofphysics,chemistryandmaterialssince 1 990s.Oneofthemostrepresentativemesoporousmaterialsismesoporoussilicapreparedbyusingalkylquaternaryammoniumcationicsurfactantsastemplate[1 3 ].Recently ,themesoporoussilicahasbecomeoneofthemostactivefieldsofhost guestass…     

复合模板剂制备介孔TiO2纳米粉体

以聚乙二醇400（PEG-400）和二乙醇胺（DEA）为复合模板剂,在室温下采用溶胶一凝胶法制备了介孔TiO2纳米粉体,并利用XRD、FE-SEM、FT-IR等方法对粉体进行了表征．结果表明：TiO2纳米粉体具有显著的介孔结构特征,400℃焙烧脱模后TiO2纳米粉体的介孔结构没有被破坏,且为单一的锐钛矿晶相;介孔TiO2纳米粉体为类球形颗粒,孔径均匀,大小约为10nm;400℃焙烧可完全去除复合模板剂．     

Center distance and pouring temperature on in-situ synthesis of WCP/Fe composite coating

Tungsten carbide (WC) particles can be in-situ synthesized through the reaction between tungsten wires and molten of gray cast iron. The different composite coatings were obtained by adjusting the pouring temperature and the center distance of tungsten wires, and were comparatively observed by X-ray diffraction, scanning electron microscopy, and two-body abrasive wear tests. The results show that the intensities of the WC peaks increase by the increasing pouring temperature, and firstly become strong and then weak by the increasing center distance. In case of the pouring temperature 1 400 °C and the center distance 0.5 mm, the formed WC particles present quadrilateral and triangle-structure and are homogenously distributed in the matrix. The wear rate of the composite coatings for stable center distance gradually increases by increasing the loads, however, at a constant pouring temperature, it firstly decreases from 5.91 to 2.97 mg/cm²·h, and slightly increases to 3.98 mg/cm²·h by increasing the center distance.     

模板剂结构和合成温度对两步法制备介孔硅结构的影响

以F108和F127为模板剂,在不添加无机盐或辅助剂情况下,采用两步法在弱酸性体系中分别制备了具有Im3m结构的SBA．16及Fm3m结构的FDU-12硅基介孔材料．采用X射线衍射（XRD）、透射电子显微镜（TEM）及氮气吸附-脱附对其进行了表征,结果显示：在此条件下制备的两种不同结构的立方介孔硅均为典型的小孔（3．57～4．26nm）厚壁（9．68～9．81nm）型硅基介孔材料．结合制备过程中反应物组成及合成温度对形成小孔厚壁型介孔材料的过程进行了讨论．对体系合成温度变化的研究表明：温度的微小变化对最终产物有序性有着很大的影响,而最终产物的结构则是由所用的模板剂结构决定的．     

Effect of surfactant/silica and hydrothermal time on the specific surface area of mesoporous materials from coal-measure kaolin

Mesoporous materials with the highest surface area were synthesized by hydrothermal treatment from coal-measure kaolin using cetyltrimethylammonium bromide(CTAB)as template.The effect of several factors on surface area of products also had been discussed.The products were characterized by FT- IR,HRTEM and N 2 adsorption and desorption isotherm plot methods.There was typical structure as Si-O,Si- OH and Si-O-Si of mesoporous materials in the framework of synthesized materials;the pore size distributions of the products showed a sharp peak at 3.82 nm.The effect of hydrothermal treatment time and the amount of template on the specific surface area of mesoporous materials was important,when the Surf/Si=0.135,and hydrothermal time=12 h,and the surface area of the product reached up to 1 070 m2/g,which was higher than other products.     

MCM-41 prepared with ionic liquid and cethytrimethylammonium bromide as co-templates

The mesoporous molecular sieves MCM-41 were prepared using room temperature ionic liquid (RTIL) synthesized in laboratory and cethytrimethylammonium bromide (CTAB) as compound templates for the first time. They were prepared under low aging temperature and short aging time. Via characterizing by XRD and nitrogen adsorption instrument, MCM-41 synthesized by this new method exhibited good crystal structure and narrow pore distribution. The following preparatory conditions was optimal: the molar ratio of RTIL to CTAB was 1.0:1.0, aging at 80 °C, for 40 h and calcined at 540 °C. It is found that the acidified MCM-41 improves its activity as catalyst over the unmodified ones. Funded by Zhengzhou Natural Science Foundation (No. 064SJZJ23115) and Key Laboratory Catalysis and Materials Science of South-central University for Nationalities Foundation     

Preparation and electrochemical properties of Pb-0.3wt%Ag/Pb-WC composite inert anodes

We prepared Pb-0.3wt%Ag/Pb-WC(WC stands for tungsten carbide,the same below) composite inert anodes by double-pulse electrodeposition on the surface of Pb-0.3wt%Ag substrates,and investigated the electrochemical properties of the composite inert anodes,which were obtained under different forward pulse average current densities from 2 A/dm~2 to 5 A/dm~2 and WC concentrations from 0 g/L to 40 g/L in bath.The kinetic parameters of oxygen evolution,corrosion potential and corrosion current of the composite inert anodes were obtained in a synthetic zinc electrowinning electrolyte of 50 g/L Zn~(2+) and 150 g/L H_2SO_4 at 35 ℃,by measuring the anodic polarization curves,Tafel polarization curves and cyclic voltammetry curves.The results show that Pb-0.3wt% Ag/Pb-WC composite inert anodes obtained under forward pulse average current density of 3 A/dm~2 and WC concentration of 30 g/L in an original acid plating bath,possess higher electrocatalytic activity of oxygen evolution,lower overpotential of oxygen evolution,better reversibility of electrode reaction and corrosion resistance in [ZnSO_4+H_2SO_4] solution.The overpotential of oxygen evolution of the composite inert anode is 0.926 V under 500 A/m~2 in [ZnSO_4+H_2SO_4] solution,and 245 mV lower than that of Pb-1% Ag alloy;the corrosion current of the composite inert anode is 0.95×10~(-4)A which is distinctly lower than that of Pb-1%Ag alloy,showing the excellent corrosion resistance.     

氨基官能化的硅基介孔材料的合成与表征

分别以十六烷基三甲基溴化铵(CTAB)和三嵌段共聚物(P123)为模板剂,正硅酸乙酯(TEOS)为硅源,合成两种硅基介孔材料MCM-41和SBA-15.通过有机硅烷偶连法将3-氨丙基三乙氧基硅烷(APTES)嫁接到已合成的两种介孔材料上,得到氨基官能化的硅基介孔材料.利用XRD、FT-IR、N2吸附-脱附和ICP含量测定对合成的材料进行表征.     

Preparation and characterization of mesoporous Al-MCM-41 layers deposited on FeCrAl metallic foils by an in-situ hydrothermal method

A new class of activated mesoporous Al-MCM-41 layers was deposited on FeCrAl metallic foils in the presence of cationic surfactant cetyltrimethylammonium bromide under basic conditions by an in-situ hydrothermal method. The characterization techniques including X-ray diffraction, nitrogen adsorption and transmission electron microscopy, as well as field-emission scanning electron microscopy were performed to investigate the pore structure and surface morphology of the Al-MCM-41 layers. The Al-MCM-41 materials are of amorphous structure but exhibit large BET surface area (up to 757.0 m²/g) and pore volume (up to 0.72 cm³/g), as well as a mean pore diameter of 3 nm. The layers deposited on the FeCrAl foils are continuous despite with a few of holes on the surface. Funded by the National Natural Science Foundation of China (No. 50502002), Scientific Research Common Program of Beijing Municipal Commission of Education (No. KM200610005016) and Youth Foundation of Beijing University of Technology (No.00190)     

One-pot Synthesis of Mesostruetured Ag/Siliea Composite Films

Mesoporous silica films embedded with Ag nanoparticles were directly synthesized by a solgel dip-coating process, combining alkyl （ethylene oxide） surfactant as temple and tetraethoxysilane as inorganic precursor. The addition of Ag^＋ ion to the reaction sol was prior to the formation of films, followed by the heat treatment at 150℃ led to the creation ofAg nanoparticies. The formation ofAg nanoparticles and the change of its surface plasma resonance absorption were characterized by Uv-vis. The small angle XRD test indicated that the films had an ordered hexagonal mesoporous structure, of which the unit cell parameter was about 4.26 nm. The TEM images and EDS spectra of the samples have directly verified the presence of mono-dispersed Ag nanoparticles within the films, due to the confine effects of mesopores.     

Preparation, Characterization and Visible Light Photocatalytic Activity of Nitrogen-doped TiO2

The N-doped TiO2 polycrystalline powder was synthesized through calcining the hydrolysis prodact of tetra-butyl titanate with ammonia. The photocatalytic activity of N-doped TiO2 powder with anatase phone calcined at 400℃ was 2.7 times higher than that of Degussa P25 for phenol decomposition under visible light. All samples had mesoporoas structures. X- ray photoelectron spectroscopy confirmed that a trace amount of N atoms remained in the anatase polycrystaUine TiO2 powder when calcined at 400 ℃ as substitutional atoms at the oxygen sites. UV-Vis and EPR analyses indicated that oxygen vacancy states were created during the course of N-doped TiO2 powder formation. It is considered that substitutional N atoms, oxygen vacancy, states, large BET surface areas and mesoporoas structure are important facwrs for the N-doped photocatalyst to present a high vis-activity.     

铁盐改性蒙脱土活化过一硫酸盐去除水中双酚A效能与机理

有机微污染物是饮用水处理的新兴难题,过一硫酸盐氧化是去除有机微污染物的有效途径,但存在催化剂成本高、制备和再生过程复杂等问题。本文尝试利用三价铁盐改性后的蒙脱土（Fe-MMT）作为过一硫酸盐催化剂,研究Fe-MMT活化过一硫酸盐（PMS）降解饮用水中双酚A的规律和效能。实验结果表明:双酚A能够快速吸附到Fe-MMT表面,并在1 h内的去除率高达96.4%。分析认为,Fe-MMT的纳米级层间距加速了Fe³⁺与PMS间的电子转移,有利于PMS活化分解产生HO·和SO₄·^-自由基,导致水中双酚A快速降解。此外,Fe-MMT的层状结构能够有效抑制水中背景腐殖酸成分对PMS活化的影响。铁盐改性蒙脱土的制备和再生过程简单,可作为过一硫酸盐催化剂应用于饮用水处理领域。     

High-performance porous carbon for supercapacitors prepared by one-step pyrolysis of PF/gelatin blends

A high-performance porous carbon material for supercapacitor electrodes was prepared by using a polymer blend method. Phenol-formaldehyde resin and gelatin were used as carbon precursor polymer and pore former polymer, respectively. The blends were carbonized at 800 °C in nitrogen. SEM, BET measurement and BJH method reveal that the obtained carbon possesses a mesoporous characteristic, with the average pore size between 3.0 nm and 5.0 nm. The electrochemical properties of supercapacitor using these carbons as electrode material were investigated by cyclic voltammetry and constant current charge-discharge. The results indicate that the composition of blended polymers has a strong effect on the specific capacitance. When the mass ratio of PF to gelatin is kept at 1:1, the largest surface area of 222 m²/g is obtained, and the specific capacitance reaches 161 F/g.     

The corrosion behavior of nano-meter embedded phase in Ti implanted H13 steel

On the SEM micrographs of Ti implanted H13 steel, a tree-branch-like structure can be observed. Further investigation with TEM shows that the newly tormed composition is a formation of nann-meter FeTi_2 phase in Ti implanted layer. The layer with a relatively high corrosion resistance has been formed in Ti implanted H13 steel with this structure.The results of electrochemical measurement show that the corrosion current density decreases obviously with an increase of ion dose. The corrosion current density in Ti implanted steel with a dose of 1.3×10~(18)/cm~2 is 8-20 times less than that of Ti implanted steel with a dose of 6×10~(17)/cm~2. The corrosion behavior of Ti implanted steel with a dose of 6×10~(17)/cm~2 could be further improved as the sample was annealed at 500℃ for 20 min and the corrosion current density decreases by 48-80 times compared to that of non-implanted samples. The corrosion trace was not observed on the annealing sample by SEM, after multi-sweep cyclic voltammetry of 40 cycles     

工业钛液制备介孔TiO2及其催化性能研究

以工业钛液为钛源,通过CTAB/P123复合模板剂形成的超分子自组装结构诱导钛的水解、缩聚得介孔TiO2前驱体,经臭氧氧化、多次萃取、分步焙烧脱模后得介孔TiO2。采用XRD、粒度分布、等温N2吸附及FT-IR等对样品进行表征。前驱体、脱模中间物及产物均为比表面积大、六方排列的锐钛型介孔结构。随着模板剂的脱除,样品的总钛含量增大,结晶度提高,产物介孔TiO2的孔径分布窄,平均孔径为3.23nm,SBET为281.5m2/g。比表面积的提高,锐钛晶型的改善及表面吸附键合的少量硫酸根等强化了介孔TiO2的催化性能,其对亚甲基蓝光催化氧化降解及乙酸乙酯酯化反应均表现出高的活性。     

Synthesis and performance of mesoporous phosphotungstic acid/alumina composite as a novel oxidative desulfurization catalyst

A series of mesoporous phosphotungstic acid/alumina composites （HPW/Al_2O_3） with various HPW contents were synthesized by evaporation-induced self-assembly method. These composites were characterized by nitrogen adsorption-desorption, TEM, FTIR, and UV-vis, and were tested as catalysts in oxidation desulfurization of model fuel composed of dibenzothiophene （DBT） and hydrocarbon, using H202 as the oxidant. These composites exhibited high activity in catalytic oxidation of DBT in model fuel and good reusing ability. The best performance was achieved by using the mesoporous HPW/Al_2O_3 with 15wt% HPW content, which resulted in a DBT conversion of 98% after 2 h reaction at 343 K, and it did not show significant activity degradation after 3 recycles. Characterization results showed that the mesoporous structure of alumina and the Keggin structure of HPW were preserved in the formed composite. These results suggested that HPW/ Al_2O_3 could be a promising catalyst in oxidative desulfurization process.     

Synthesis and characterization of VO<Subscript>2</Subscript>/mesoporous carbon composites for hybrid capacitors

VO₂/ordered mesoporous carbon (CMK-3) composites were prepared by solid-state reaction process. The microstructures were characterized by X-ray diffraction (XRD), nitrogen adsorption and desorption, field-emission scanning electron microscopy (FE-SEM) and transmission electron microscopy (TEM). The experimental results showed that the vanadium oxide in the composites was vanadium dioxide (VO₂) with monoclinic structure, which was artificially loaded on the outer surface of CMK-3. VO₂/ordered mesoporous carbon composites present a significantly improved capacitive performance (131 F/g) increased by 40.86% compared to that of CMK-3 carbon (93 F/g). Therefore, as-prepared VO₂/mesoporous carbon composites suggest promising applications in hybrid capacitors.     

Road performances of mesoporous nano-silica modified asphalt binders

The objective of this paper was to find new modifier to improve the aging resistance and low temperature cracking resistance of asphalt. To investigate the aging resistance of modified asphalt binders, mesoporous nano-silica(doping Ti~(4+)) was used as a asphalt modifier. Some physical properties including penetration, ductility, and softening point of asphalt were analyzed with RTFO(Rotating thin film oven) aging and ultraviolet aging. Moreover, the performances of high and low temperature of modified asphalt binders with pressure aging were tested by dynamic shear rheometer(DSR) test and bending beam rheometer(BBR) test. These results showed that the penetration decreased, low temperature ductility, and softening point increased when adding mesoporous nano-silica to base asphalt. After ultraviolet radiation aging, the penetration loss and ductility loss of modified asphalt decreased than that of original asphalt, the increase of softening point was also significantly reduced than that of base asphalt. Furthermore, The test results of DSR and BBR showed that the G*sinδ and creep modulus‘s' of pressure aged asphalt decreased, but the creep rate ‘m' increased. It can be concluded that the aging resistance and cracking resistance of modified asphalt are improved by adding mesoporous nano-silica, especially the doping of Ti~(4+) could improve the aging resistance obviously.