Production of a high dispersion of silver nanoparticles on surface-functionalized multi-walled carbon nanotubes using an electrostatic technique

Multi-walled carbon nanotube/silver nanoparticles hybrid materials were easily synthesized by a mixing method of acid-oxidized nanotubes and the colloidal dispersion of silver nanoparticles. The silver colloidal dispersion was pre-synthesized by a chemical reduction of silver nitrate by dimethyl sulfoxide in the presence of trisodium citrate dihydrate as capping agents. In the mixing method, approx 5.0 nm diameters of silver nanoparticles with face-centered cubic crystal structures are highly dispersed on the acid-oxidized nanotubes due to the surface reactivity resulting from the enhancement of oxygen-containing functional groups. The results emphasize that the anchoring effect of the functionalized nanotube surface on silver nanoparticles originates from electrostatic metal-support interactions.     

双模板结构导向剂制备有序介孔炭

以间苯二酚/甲醛制备的酚醛树脂为碳前躯体,三嵌段共聚物F127和P123作为主辅结构导向剂,采用有机-有机自组装的方法制备有序介孔炭(Ordered mesoporous carbons,简称OMCs)。采用X射线衍射仪、透射电镜和N2吸/脱附手段对所制OMCs进行表征,研究了反应时间以及主辅模板剂的比例对介孔孔道结构的影响。结果表明,随着反应时间从24h延长至72 h,介孔炭有序性先增后减;当主辅模板剂F127/P123摩尔比为0.002 7∶0.002 7时,所得介孔炭有序性较好,为P6mm型孔道结构,介孔孔容和比表面积分别为0.59 cm3/g和640.34 m2/g,平均孔径为3.68 nm.     

结构有序、双重孔隙中孔炭材料的合成与表征

采用纳米涂层技术,以介孔分子筛SBA 15为模板,在其纳米孔道内引入糠醇/草酸溶液,经原位聚合,炭化后制得炭/SBA 15复合物。采用化学法脱除模板后制得具有规则结构的中孔炭。高分辨TEM表征结果显示该中孔炭是由纳米炭管相互联接、堆积而成,且具有六方对称结构。氮吸附结果显示其比表面积高达2000m2/g,孔径呈双峰分布。孔径相对较大的孔隙来源于SBA 15孔道经纳米涂层后所保留的孔隙;孔径相对较小的孔隙来源于SiO2移除后遗留的纳米孔空间。该方法可应用于以其他多孔氧化硅为模板制备新型纳米复合物的研究过程。     

非水体系快速挥发法直接合成有序介孔炭

采用非水溶剂快速挥发法,以表面活性剂和酚醛树脂为结构导向剂和碳前驱体制备介孔炭.通过透射电镜、氮吸附-脱附和扫描电镜对产品的结构进行了表征.结果表明:所制介孔炭具有高度有序的二维六方结构.表面活性剂与酚醛树脂的配比对介孔炭的有序性有较大的影响,当其质量比高于1:0.25时,可保持良好的有序度.随着比值的减小,有序度逐渐降低.与蔗糖液相浸渍法相比,非水体系快速挥发法所制介孔炭具有较少的外微及大孔.     

印刻法制备中间相沥青基中孔炭

用中间相沥青作碳源,硅胶水溶液作造孔剂,采用胶体印刻法制得一系列中孔碳。实验发现当适量纳米级硅源添加到中间相沥青中,会在彼此颗粒间形成一定的纳米孔道,从而导致中间相沥青在炭化过程中没有沥青由固相向液相转化的过程。结果表明：碳硅比、印刻温度以及中间相沥青的基本物化性质都将对中孔碳的孔结构发生重要影响。且制得比表面积和孔容分别为482m2/g和1.62cm3/g的中孔碳。     

Nickel nanoparticles decoration of ordered mesoporous silica thin films for carbon nanotubes growth

We report in situ successive depositions of nickel nanoparticles and carbon nanotubes (CNTs) on ordered mesoporous silica films used as template for the catalyst particles. The mesoporous films are synthesized by the evaporation-induced self-assembly process from tetraethyl orthosilicate derived oligomers and a di-block copolymer from dip-coating deposition method. The substrates are decorated with Ni nanoparticles through Ion Beam Deposition and posterior annealing to induce metal coalescence in the mesoporous cavities. CNTs were then grown by Chemical Vapor Deposition in the presence of an electric field. These techniques provide a simple control method producing ordered arrangements of catalyst nanoparticles and ordered nanostructures for large area applications.     

High-density assembly of gold nanoparticles to multiwalled carbon nanotubes using ionic liquid as interlinker

Gold nanoparticles were deposited onto the surface of carbon nanotubes through an interlinker of ionic liquid terminated with hydroxyethyl units at one end and exchangeable chloride counterions at the other end. The morphology, structure, and composition of the resulting hybrids were characterized by transmission electron microscopy and X-ray diffraction. A very high density of gold nanoparticles was homogeneously dispersed and well-separated from one another on the modified multi-walled carbon nanotubes. The optical absorption of the products was observed by UV-visible spectroscopy. The results imply that the obtained carbon nanotube-gold nanocomposites have a good application potential in catalysis, sensor, and fuel cells.     

Surface modification of carbon nanofibers with platinum nanoparticles using a “polygonal barrel-sputtering” system

Carbon nanofibers (CNFs) modified with Pt nanoparticles have been prepared using a new RF sputtering instrument called a “polygonal barrel-sputtering” system. The prepared samples were characterized by optical microscopy, field emission scanning microscopy (FE-SEM), inductively coupled plasma atomic emission spectrometry (ICP-AES), X-ray fluorescence (XRF), X-ray diffraction (XRD), and transmission electron microscopy (TEM) with energy-dispersive X-ray spectrometry (EDS). When only the CNFs were placed in the system, large CNF aggregates with sizes of 5-15 mm were observed and Pt was deposited non-uniformly. In addition, microscopic observations revealed that ca. 40% of the CNFs were still unmodified. In contrast, when pieces of bent columnar stainless steel were placed in the system with the CNFs, large CNF aggregates were not observed in the Pt deposited sample. In this sample, CNFs modified with highly dispersed Pt nanoparticles were obtained successfully, and unmodified CNFs were absent. The sizes of the Pt nanoparticles were in a narrow range of 1.7-3.5 nm, and their mean size was 2.5 nm.     

模板法制备沥青烯基有序结构中孔炭

以煤炭直接液化工艺过程的副产物--沥青烯为碳源,中孔硅分子筛SBA-15为模板,采用模板炭化法制备了具有规则结构的中孔炭.制备过程包括利用溶剂夹带法将沥青烯填充到模板孔道内,炭化模板孔道内的沥青烯以及脱除模板等步骤.利用扫描电镜、透射电镜、粉末X射线衍射仪对产品的微观形貌和结构进行了分析;测定了材料的抗氧化性能、导电性能以及对N2的吸附特性.结果表明:产品具有对模板结构反转复制的规则结构,其比表面积为562m2/g,孔容为0.566cm3/g,孔尺寸呈单分布,平均孔径为3.57nm;此外,材料具有良好的抗氧化性能,空气环境下300℃处理后样品仍保持规则的孔结构形态;其平均电阻率为0.16Ω*cm左右,属半导体材料导电性能范畴.     

Fabrication of mesoporous carbonated hydroxyapatite microspheres by hydrothermal method

Mesoporous carbonated hydroxyapatite microspheres (MCHMs) have been converted from calcium carbonate microspheres (CCMs) by hydrothermal method. After soaking the CCMs in disodium hydrogen phosphate solutions, carbonated hydroxyapatite nanoparticles are formed via a dissolution-precipitation reaction. X-ray diffraction (XRD) and Fourier-transform infrared spectroscopy (FTIR) reveal that the as-obtained samples are calcium deficient hydroxyapatite with B-type CO₃²⁻ substitution. The transmission electron microscopy (TEM) indicates that the MCHMs are composed of many nanoparticles within the whole microspheres. These nanoparticles aggregate to form mesopores with a pore size of 4.5-14.0 nm among them. The formation mechanism of MHAMs has been discussed.     

介孔炭作为加氢脱硫催化剂载体材料的研究

以介孔硅SBA-15为模板,焦糖和呋喃醇为碳源,通过多种浇注法制备介孔炭材料.采用低温氮吸附、透射电镜和X射线小角衍射分析模板及介孔炭的织构.结果显示合成的介孔炭成功地复制了SBA-15的结构.以制备的介孔炭作载体担载钴钼合成了加氢脱硫催化剂,利用X射线能谱、透射电镜能量分布谱及一氧化氮化学吸附评估了催化剂的活性及活性点分布,结果表明介孔炭担载的催化剂活性高于活性炭担载的同类催化剂.     

双电层电容器用中孔炭微球/活性炭复合电极的制备

采用水热法合成比表面积1850m2/g、粒径lμm的中孔炭微球(MCM);而后将所制MCM加入比表面积为3200m2/g的超级活性炭(HSAC)中制成用于双电层电容器的复合电极材料,并研究了该复合电极材料的电化学性能.结果表明:在比表面积为3200m2/g的HSAC中添加质量分数20%的MCM后,其颗粒接触内阻、离子扩散内阻明显降低;在6mol/L的KOH电解液体系中,在12A/g的电流密度下,其比电容仍能稳定在230F/g.而在同样的条件下,纯HSAC和纯MCM的比电容仅分别为190F/g和148F/g.复合电极在大电流下电化学性能的提高应归因于MCM合适的粒径、中孔结构及其较高的比表面积.     

The effect of carbon precursor on the pore size distribution of mesoporous carbon during templating synthesis process

The starch and cyclodextrin were selected as the precursors and the mixture of surfactant and tetraethyl orthosilicate (TEOS) as template to prepare mesoporous carbon. The result showed that a bimodal pore size distribution in mesoporous carbon derived from starch appeared; one was around 3.4 nm and the other ranged from 3.8 to 16.2 nm. However, there existed a concentrated pore size distribution from 3.2 to 4.2 nm in mesoporous carbon derived from cyclodextrin. The different molecular structure of starch and cyclodextrin and their polymerization process in the presence of sulfur acid were responsible for the resulted mesoporous carbon structure; the starch could polymerize by head to head or side by side, but the cycleodextrin was only polymerized by head to head.     

Efficient desulfurization of fuel with functionalized mesoporous carbon CMK-3-O and comparison its performance with mesoporous carbon CMK-3

In this work, a functionalized mesoporous carbon (CMK-3-O) was synthesized after oxidation with nitric acid and was used to adsorb dibenzothiophene (DBT) from model oil for the first time. Then, its performance was compared with that of CMK-3. The functionalized mesoporous carbon, CMK-3-O, showed better a capacitance performance for DBT adsorption than that of CMK-3. The maximum adsorption capacity was obtained for functionalized mesoporous carbon at optimum conditions with 6 M HNO₃ aqueous solution and 30 min contact time. The physical and structural properties of CMK-3-O and CMK-3 were investigated with X-ray diffraction method (XRD), N₂ adsorption–desorption isotherm, FT-IR, and elemental analysis (CHNO). Results of the elemental analysis showed that the oxygen and nitrogen content has increased and the carbon content has decreased through oxidation treatment. The effects of various factors on the adsorption process (such as temperature, amount of adsorbent, contact time, and concentration) of DBT were studied. CMK-3-O showed a maximum adsorption capacity of 86.96 mg DBT g^?1 of CMK-3-O at optimized conditions (temperature, 25°C; adsorbent dosage, 20 g L^?1; contact time, 60 min), which was a higher adsorption capacity of that observed for CMK-3 (57.47 mg DBT g^?1 of CMK-3). Kinetic studies have revealed that the adsorption of DBT can be described by a pseudo-second-order rate equation. Equilibrium data showed that adsorption process was best represented by the Langmuir model. The results also illustrated the fact that the regenerated adsorbent afforded 64.3% of the initial adsorption capacity after the two regeneration cycles.     

Short-period synthesis of ordered mesoporous silica SBA-15 using ultrasonic technique

Mesoporous silica SBA-15 was synthesized from rice husk ash via the ultrasonic technique in the hydrolysis-condensation stage. The effect of the time period in this stage on the mesoporous silica SBA-15 structure and physical properties was investigated and compared with those of the SBA-15 prepared by the conventional technique. It has been shown that the ultrasonic technique can be successfully applied for the synthesis of mesoporous silica SBA-15 with highly ordered hexagonal pore-arrangement and narrow PSD within the much shorter hydrolysis-condensation period. The SBA-15 products synthesized via the ultrasonic technique for the time period of 3 h have higher specific surface area, total pore volume, and microporosity than those prepared by the conventional technique for the time period of 24 h.     

Preparation of mesoporous carbon from biomass for heavy metal ion adsorption

Mesoporous carbon (MC-S) has been synthesized via a facile hydrothermal method by using cheap and nontoxic soluble starch as carbon precursor, Pluronic copolymer as soft templates. In the process of hydrothermal synthesis, the soluble starch can hydrolyze to give glucose, which can assemble with Pluronic copolymer through hydrogen bond interactions. Glucose further dehydrates and cross-links to form polymer networks. After carbonization of the polymer networks, MC-S can finally be obtained. The obtained MC-S has a specific surface area of 439 m² g^?1, uniform pore size of 4.5 nm as well as high oxygen content of 23.32%. The MC-S exhibits a good adsorption for heavy metal ions superior to FDU-15 due to the oxygen functional groups.     

介孔炭材料应用于电化学催化的研究进展

由于介孔炭材料具有高比表面、均一可调的孔径尺寸和形貌、良好的导电性和化学稳定性等优点,已被广泛应用到催化、吸附、分离和电化学储能等领域.近年来,多组分的掺杂与复合使介孔炭材料拥有可调变的功能性,已成为材料领域研究的一个热点.本文首先介绍介孔炭材料的合成,包括软模板法、硬模板法和无模板法等.接着论述介孔炭及其复合材料在电...     

表面活性剂改性的大孔径介孔炭对电极染料敏化太阳电池(英文)

以大孔径的介孔炭(MC)为催化层材料经低温热处理构建出炭对电极,着重探讨了在炭浆料中添加Triton X100对其组装的染料敏化太阳电池(DSCs)光电性能的影响,并引入分形维数(DF)用于定量评估炭膜形貌的差异。结果表明,当炭浆料中Triton X100的含量增加到0.1 mL(相应MC含量为0.6 g)时,DSCs的光电转换效率增加至5.65%,其值比活性炭对电极DSCs高46.5%,且达到Pt对电极DSCs的95.4%。Triton X100改性的介孔炭对电极的高性能归功于高品质的炭膜和介孔炭本身合理的孔结构(如大尺寸孔径和大比表面积等)。相对于未添加Triton X100的纯介孔炭对电极,Triton X100改性的介孔炭对电极具有分布更均匀的炭膜和更小的分形维数,是对电极欧姆串阻减小及相应器件效率改善的一个重要因素。     

以纳米SO_2粒子为模板由不同炭前躯体制备中孔炭(英文)

以纳米SO2粒子为模板,酚醛树脂、中间相沥青和聚丙烯腈为炭前躯体制备中孔炭。利用氮气吸附、元素分析和X-射线光电子能谱等分析了不同种类炭前躯体对中孔炭的影响。结果表明:在炭化温度和纳米粒子添加量相同的情况下,不同炭前躯体所制中孔炭的孔结构和表面化学性质不同。中间相沥青基中孔炭中微孔和中孔含量最少,酚醛基中孔炭中含有丰富的微孔和中孔,聚丙烯腈基中孔炭中含有大量的含氮官能团。     

Nonionic surfactant-templated mesoporous carbon as an electrocatalyst support for methanol oxidation

Two carbons were synthesized for use as platinum electrocatalyst supports for methanol oxidation. For both materials, furfuryl alcohol was used as the carbon precursor; however, one (CPEG) was made using poly ethylene glycol as the pore former, while the other (CSRF) was produced using Pluronic^® F127 as the soft template by organic–organic self-assembly. The CPEG and CSRF carbons were estimated from nitrogen physisorption experiments to be micro- and mesoporous, respectively. Platinum nanoparticles were deposited on each carbon as well as on Vulcan XC-72 carbon by the formic acid reduction method. The physicochemical properties of electrocatalysts were studied using X-ray diffraction (XRD), transmission electron microscopy (TEM), and energy dispersive X-ray analysis (EDX), and their electrochemical features were examined using cyclic voltammetry, chronoamperometry, and impedance spectroscopy. It was found that higher methanol oxidation peak current densities as well as lesser charge transfer resistance at electrode/electrolyte interface were obtained for Pt supported on CSRF as compared to those on Vulcan XC-72 carbon, owing to the higher specific surface area and larger total pore volume (696 m² g⁻¹ and 0.60 cm³ g⁻¹, respectively) together with superior electrical conductivity of mesoporous CSRF. On the other hand, the lower surface area and pore volume of microporous CPEG substrate confined Pt nanoparticles deposition and thus made CPEG-supported Pt an inefficient methanol oxidation electrocatalyst.