有序介孔碳载金属催化剂用于择形催化

择形催化在精细化学合成等领域发挥着重要作用。有序介孔材料具有相对大的孔径以及规整的孔道结构,探究其在有机合成中择形催化性能具有重要意义。本研究考察了有序介孔碳载AuPd合金催化剂的孔径对苄醇选择氧化和喹啉选择加氢反应中分子尺寸选择催化性能的影响。结果表明：有序介孔碳催化剂介孔孔径与反应物分子尺寸之间存在明显的正依存关系。苯甲醇和喹啉等尺寸较小的底物分子可扩散进入3.5 nm的介孔孔道,在合金表面反应;而尺寸较大的分子如2-甲基苄醇和3,5-二叔丁基苄醇,内扩散受到限制,几乎不能发生转化。当孔径扩大至5.0nm时,2-甲基苄醇可扩散进入孔道,催化氧化的转化频率(TOF_Pd)可达307 h^-1;进一步扩大孔径至6.0 nm,尺寸更大的分子如3,5-二叔丁基苄醇也能被氧化,TOF_Pd达到140 h^-1。     

水热法磷掺杂介孔碳的制备与表征

以磷酸为磷源,三嵌段共聚物F127为软模板,通过简单的低温水热法制备了磷掺杂介孔碳(PMCs)。通过透射电镜、能谱仪等多种测试方法以研究磷掺杂对介孔碳形貌结构的影响,利用电化学工作站研究对性能的影响。结果表明,所制备的复合材料PMC-4的比表面积为645.95 m²/g,平均孔径为4.0 nm。电化学测试表明,通过调整磷掺杂量可获得最大比电容。在电流密度为0.5 A/g下,PMC-4容量可达172 F/g。磷原子的引入能提高介孔碳的电催化活性,增强电解质和电极之间界面的润湿性以改善介孔碳的电化学性能,合成的磷掺杂介孔碳材料可作为很有潜力的电极材料。     

简易模板法制备有序介孔碳及其表征

目前制备有序介孔碳的方法工艺复杂、繁琐耗时,为了简化其制备工艺,缩短实验流程,本文提出一种不需要添加额外溶剂直接制备有序介孔碳的方法。以三嵌段共聚物F127为模板剂,自制低分子量酚醛树脂为碳前体,制备了具有二维六方结构的介孔碳。采用红外光谱对酚醛树脂和F127进行表征,研究了两者之间的作用力;采用X射线衍射、透射电镜和N2吸附/脱附等手段对介孔碳结构进行表征,研究了酚醛树脂的合成温度和模板剂用量对介孔碳结构的影响。结果表明酚醛树脂合成温度为70℃,F127：PF=1时,得到的介孔碳比表面积、孔容和孔径分别为490m2/g、0.41cm3/g和4.15nm。     

模板法壳聚糖基介孔碳材料的制备与表征

以壳聚糖为碳前驱体、正硅酸乙酯为模板硅源,利用模板法制备了介孔碳材料。通过N2吸附/脱附、XRD、TEM等手段对介孔碳结构进行了表征。考察了溶液pH值和硅碳比对介孔碳孔结构的影响,介孔碳对维生素B12的吸附性能。结果表明,介孔碳材料孔隙发达、呈蠕虫状孔结构;溶液pH值为4、硅碳比为0.9时,介孔碳的比表面积、孔容及平均孔径分别达到1 118 m~2/g,1.48 cm~3/g及5.3 nm;对VB_(12)分子的吸附过程符合Langmuir单分子层吸附模型,最大平衡吸附量达到417.8 mg/g,2 h吸附量达到平衡吸附量的87.4%。     

模板法壳聚糖基介孔碳材料的制备与表征

以壳聚糖为碳前驱体、正硅酸乙酯为模板硅源,利用模板法制备了介孔碳材料。通过N2吸附/脱附、XRD、TEM等手段对介孔碳结构进行了表征。考察了溶液pH值和硅碳比对介孔碳孔结构的影响,介孔碳对维生素B12的吸附性能。结果表明,介孔碳材料孔隙发达、呈蠕虫状孔结构;溶液pH值为4、硅碳比为0.9时,介孔碳的比表面积、孔容及平均孔径分别达到1 118 m²/g,1.48 cm2/g,1.48 cm³/g及5.3 nm;对VB_(12)分子的吸附过程符合Langmuir单分子层吸附模型,最大平衡吸附量达到417.8 mg/g,2 h吸附量达到平衡吸附量的87.4%。     

硫氮掺杂介孔碳材料的合成与表征

本实验采用水热法合成了ZIF-8,再将其与硫酸铵混合后,在氩气和氢气氛围下,经高温热解,合成了硫氮掺杂的介孔碳材料S-N-C。采用SEM、XRD、Raman、XPS等手段对该材料的形貌、结构、元素组成等进行了表征,确定产物为一种掺硫量为0.623%、氮掺杂量为2.89%的介孔碳材料。本方法可为掺杂材料的合成提供一种新思路。     

壳聚糖基介孔碳的制备研究进展

介孔碳材料具有比表面积大、孔径可调、表面易修饰以及化学稳定性好等优点,被广泛应用于工业、能源以及医药等领域.综述了近年来壳聚糖基介孔碳的制备方法,并根据存在的问题,展望了其今后的发展方向.     

介孔分子筛固载催化剂的制备研究

实验制备了介孔分子筛固载催化剂Co-MCM-41,并通过XRD、SEM、TEM分析,表征了介孔分子筛颗粒的粒径、晶型、光谱特征等情况。通过实验数据证明,摩尔比为Co：Si=0.05：1时微波水热法合成的分子筛粉体具有最优的比表面积和平均孔径,可作为催化剂材料。     

介孔碳球的制备研究进展

作为一类新型球形介孔碳材料,介孔碳球具有较大的比表面积及孔容、可调的孔径、易于修饰的表面、良好的化学稳定性和机械性等特性,因此在环境治理、能量储存与转化、生物医药、催化应用和功能材料等领域有着巨大的应用潜力.综述了模板法、St?ber法、水热碳化法、微乳聚合法以及组合法等制备介孔碳球的相关研究,提出了介孔碳球在制备方面...     

木质素基介孔碳材料的制备及应用进展

木质素是自然界中唯一可提供再生性芳香基化合物的非石油类资源,酚羟基的可替代性、低成本及其高含碳量使其成为合成可持续介孔碳的优选前体。本文分别介绍了采用硬模板法、软模板法、双模板法、活化法、水热法以及溶胶-凝胶法制备木质素基介孔碳材料的最新研究进展。分析对比了采用不同方法制备的介孔碳材料所具有的孔道结构和形貌特点,并详细说明了其在吸附、催化、药物缓释和超级电容器等主要方面的应用。最后根据木质素基介孔碳材料在制备及应用过程中所面临的困境,提出发展一种简单、绿色、低成本的合成方法用以制备新型介孔结构的高性能复合型木质素基介孔碳材料将成为今后主要的研究方向。     

Copper nanoparticles/polyaniline-derived mesoporous carbon electrocatalysts for hydrazine oxidation

Copper nanoparticles-decorated polyaniline-derived mesoporous carbon that can serve as noble metal-free electrocatalyst for the hydrazine oxidation reaction (HzOR) is synthesized via a facile synthetic route. The material exhibits excellent electrocatalytic activity toward HzOR with low overpotential and high current density. The material also remains stable during the electrocatalytic reaction for long time. Its good electrocatalytic performance makes this material a promising alternative to conventional noble metal-based catalysts (e.g., Pt) that are commonly used in HzOR-based fuel cells.

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Graphitized mesoporous carbon supported Pt-SnO2 nanoparticles as a catalyst for methanol oxidation

A mesostructured composite catalyst, Pt-SnO₂ supported on graphitized mesoporous carbon (GMC), has been prepared and its electrochemical activity for methanol oxidation has been investigated. The materials were characterized by XRD, FESEM, TEM, EDX spectrum and N₂ sorption techniques. Cyclic voltammetry, chronoamperometry and steady-state polarization tests were adopted to characterize the electro-catalytic activities of the materials for methanol oxidation. The results show that, the overall methanol electro-oxidation catalytic activity of the mesostructured composite catalyst, 20 wt.% PtSnO₂ (1:1, mass ratio)/GMC, is obviously higher than that of 20 wt.% PtSnO₂/C with commercial carbon black as support under the same loading amount of Pt-SnO₂ catalysts, and is also much higher than that of commercial catalyst 20 wt.% Pt/C at half Pt using amount.     

中孔碳负载铂催化剂制备及其催化3,4-二氯硝基苯加氢反应

以糠醇为碳源,在酸性中孔模板剂MSU-S上缩合,合成具有中孔结构碳材料(MC),通过浸渍法合成Pt/MC催化剂。采用XRD、BET、SEM和TEM等手段对MC和Pt/MC进行表征,MC富含中孔,有效分散Pt纳米粒子并在反应过程中稳定Pt。研究Pt/MC对3,4-二氯硝基苯催化加氢反应的催化性能,在3,4-二氯硝基苯 1 mmol、催化剂用量100 mg、乙醇5 mL、反应温度30 ℃、常压氢气和反应时间6 h条件下,3,4-二氯硝基苯转化率达100%,3,4-二氯苯胺选择性达99.7%,Pt/MC重复使用5次,催化性能保持不变。     

Platinum and platinum-ruthenium nanoparticles supported on ordered mesoporous carbon and their electrocatalytic performance for fuel cell reactions

Highly ordered meso-porous carbon, denoted CMK-3 was synthesized by using mesoporous silicates, SBA-15 as the starting templating materials. The ordered mesoporous carbon was loaded with platinum and platinum-ruthenium nanoparticles using alternative synthesis techniques. The metal loaded ordered mesoporous carbon powders were characterized by transmission electron microscopy (HRTEM), energy dispersive X-ray analysis (EDX), X-ray diffraction, and nitrogen adsorption isotherm experiments. Micrometer-scale and centimeter-scale electrodes containing the mesocarbon/nanometal electrocatalysts were tested for some typical fuel cell reactions. While the nanometal/mesocarbon catalysts have well-defined and uniform properties in the nanometer scale, they have mixed electrocatalytic performance. A synthesized Pt/mesocarbon electrocatalyst outperformed a commercial electrocatalyst for oxygen reduction on a gas-diffusion electrode. The Pt-Ru/mesocarbon electrocatalyst synthesized, however, was not as effective for methanol oxidation.     

Platinum supported on resorcinol–formaldehyde based carbon aerogels for PEMFC electrodes: Influence of the carbon support on electrocatalytic properties

Two carbon aerogels with different nanopore size distributions but both with high surface area, high nanoporous volume and low bulk density have been compared as platinum support. The influence of the nanostructure of the carbon aerogel on the platinum nanoparticle deposit was investigated. The platinum was deposited on the carbon by means of two different techniques, one employing an anionic platinum precursor, the other using a cationic one. The porosity of the carbon aerogels was characterized by combining N₂-sorption and mercury porosimetry. The platinum deposit was characterized by transmission electron microscopy and rotating disk electrode experimentation to measure the platinum active surface area and its activity towards oxygen reduction reaction (ORR). The structural differences between the carbon aerogels did not yield any difference in platinum deposits in terms of Pt-surface area and ORR activity. Interestingly, the ORR mass activity of the high Pt-surface area samples, obtained by the cationic insertion technique, was several times lower than that of the samples obtained by the anionic technique. This observation was attributed to the particle size effect, detrimental in the case of platinum particle size around 1 nm.     

Pt–Ru nanoparticles supported on functionalized carbon as electrocatalysts for the methanol oxidation

Platinum–ruthenium alloy electrocatalysts, for methanol oxidation reaction, were prepared on carbons thermally treated in helium atmosphere or chemically functionalized in H₂O₂, or in HNO₃ + H₂SO₄ or in HNO₃ solutions. The functionalized carbon that is produced using acid solutions contains more surface oxygenated functional groups than carbon treated with H₂O₂ solution or HeTT. The XRD/HR-TEM analysis have showed the existence of a higher alloying degree for Pt–Ru electrocatalysts supported on functionalized carbon, which present superior electrocatalytic performance, assessed by cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy, as compared to electrocatalysts on unfunctionalized carbon. It also was found that Pt–Ru alloy electrocatalysts on functionalized carbon improve the reaction rate compared to Pt–Ru on carbons treated with H₂O₂ solution and thermally. A mechanism is discussed, where oxygenated groups generated from acid functionalization of carbon and adsorbed on Pt–Ru electrocatalysts are considered to enhance the electrocatalytic activity of the methanol oxidation reaction.     

Preparation and electrocatalytic application of high dispersed Pt nanoparticles/ordered mesoporous carbon composites

A simple approach for the synthesis of nanosized platinum particles supported on ordered mesoporous carbons (OMCs) was described. For the first time, we successfully used the positively charged poly-(diallydimethylammonium chloride, PDDA) to wrap OMCs and attached Pt nanoparticles (OMCs–PDDA/Pt) via electrostatic interaction. The obtained OMCs–PDDA/Pt nanocomposites were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and electrochemical methods. TEM images reveal that the Pt nanoparticles with an average size of ∼2.88 nm are uniformly dispersed on the surface of OMCs–PDDA. The electrocatalytic behavior of OMCs–PDDA/Pt modified glassy carbon (GC) electrode was investigated by cyclic voltammetry, current–time and chronoamperometry methods using hydrazine as a redox probe. The electrochemical results indicate that the OMCs–PDDA/Pt exhibit a good electrocatalytic activity toward the oxidation of hydrazine than that of OMCs/Pt. All these electrochemical measurements confirm the fact that the OMCs–PDDA/Pt nanocomposites may have applications in biological and environmental sensors.     

The inclusion of Mo, Nb and Ta in Pt and PtRu carbon supported electrocatalysts in the quest for improved CO tolerant PEMFC anodes

The effect of the inclusion of Mo, Nb and Ta in Pt and PtRu carbon supported anode electrocatalysts on CO tolerance in proton exchange membrane fuel cells (PEMFC) has been investigated by cyclic voltammetry and fuel cell tests. CO stripping voltammetry on binary Pt_xM/C (M: Mo, Nb, Ta) reveals partial oxidation of the CO adlayer at low potential, with PtMo (4:1)/C exhibiting the lowest value. At 80 °C, the operating temperature of the fuel cell, CO oxidation was observed at potentials close to 0 V versus the reversible hydrogen electrode (RHE). No significant difference for CO electro-oxidation at the lower potential limit, compared to PtRu/C, was observed for PtRuM_y/C (M: Mo, Nb). Fuel cell tests demonstrated that while all the prepared catalysts exhibited enhanced performance compared to Pt/C, only the addition of a relatively small amount of Mo to PtRu results in an electrocatalyst with a higher activity, in the presence of carbon monoxide, to PtRu/C, the current catalyst of choice for PEM fuel cell applications.     

熔盐法合成有序介孔碳负载的金属碳化物

有序介孔碳是一种具有宽孔径、规则孔道结构、高比表面积和大孔容的纳米结构材料,具有很高的导电性及化学稳定性,是一种非常优良的载体材料。过渡金属碳化物因其结构相似性,具有一系列类似贵金属的性质,可作为贵金属替代材料,用于多相催化过程。但过渡金属碳化物多数粒径大、比表面积低,不利于催化活性,因此,采用熔盐法合成了多种有序介孔碳负载的过渡金属碳化物,并通过SEM、TEM、XRD、BET等方法对样品进行了一系列表征。结果表明,该方法能有效制备碳负载的TiC、Mo₂C等金属碳化物,且具有较小的颗粒尺寸和较高的比表面积,将有较好的催化应用前景。