Preparation of polyaniline‐coated mesoporous carbon and its enhanced electrochemical properties

Polyaniline/MC (mesoporous carbon) composite was synthesized by in situ chemical polymerization method and was used as a new electrode material for supercapacitor. The composite was characterized by N₂ adsorption and scanning electron microscope. The electrochemical capacitance performance of the composite was investigated by cyclic voltammetry (CV) and galvanostatic charge–discharge tests with a three‐electrode system in a 10 wt% H₂SO₄ solution. The polyaniline/MC composite electrode shows much higher specific capacitance than pure MC electrode, which is attributed to the incorporation of polyaniline onto the pore surface of MC. Copyright © 2009 John Wiley & Sons, Ltd.     

有序中孔炭的制备及电性能研究

采用微湿含浸法制备了一系列具有不同比表面积和孔径分布的超级电容器有序中孔炭材料,同时采用Al-SBA-15为模板剂制得具有六方排列的空心炭管CMK-5.所制得的有序中孔炭的BET比表面积随糠醇加入量的增加而减小.电化学性能测试结果表明,在1mA·cm-2的充放电电流密度下各中孔炭材料比电容的大小顺序与其BET比表面积的大小顺序相一致.在所有样品中AlSC-0.8由于具有最大的比表面积,因此其比电容最大,达87.8F·g-1.倍率性能测试结果表明,具有CMK-3结构的SC-2.0的倍率性能最好,在50mA·cm-2的放电电流密度下其放电比电容接近AlSC-0.8有序中孔炭的水平.     

Ionothermal synthesis of crystalline, condensed, graphitic carbon nitride

Herein we report the synthesis of a crystalline graphitic carbon nitride, or g-C(3)N(4), obtained from the temperature-induced condensation of dicyandiamide (NH(2)C(=NH)NHCN) by using a salt melt of lithium chloride and potassium chloride as the solvent. The proposed crystal structure of this g-C(3)N(4) species is based on sheets of hexagonally arranged s-heptazine (C(6)N(7)) units that are held together by covalent bonds between C and N atoms which are stacked in a graphitic, staggered fashion, as corroborated by powder X-ray diffractometry and high-resolution transmission electron microscopy.     

热解条件对氮杂有序介孔炭材料电催化性能的影响

氧还原反应是燃料电池及金属空气电池中极其重要的电化学反应之一,贵金属铂基催化剂被认为是最有效的氧还原反应电催化剂.然而,贵金属铂的资源稀缺以及高成本问题阻碍了相关技术的大规模应用,探索发展廉价高效的贵金属替代型催化剂是推动燃料电池发展的根本解决方案.近年来,人们在非贵金属催化剂开发方面取得了显著进展,其中新型纳米结构掺杂炭材料研究尤为活跃.氮杂有序介孔炭材料由于其高比表面积和独特的孔结构,在燃料电池技术上具有广泛的应用前景.在氮杂有序介孔炭材料的制备过程中,热解条件对炭材料组成、结构及电催化性能有着重要影响.然而,目前尚未见对氮杂炭材料制备过程中热解条件的影响进行系统研究.
　　本文采用我们发展的蒸汽化-毛细管冷凝法,以SBA-15为硬模板浸渍前驱体吡咯,制备出具有高比表面积和独特孔结构的氮杂有序介孔炭材料,系统研究了热解条件(包括热解温度、热解时间和升温速率)对炭材料组成、结构及电催化性能的影响,采用N2吸附-脱附等温线、X射线光电子能谱(XPS)及Raman光谱等方法考察了氮杂有序介孔炭材料的结构和组成,采用循环伏安法与旋转环盘电极研究了其电化学行为与氧还原反应电催化活性及选择性.
　　N2吸附-脱附等温线显示,氮杂炭材料对应IV型吸附-脱附等温线,孔径主要分布在2–10 nm,表明所制材料具有介孔结构.随着热处理温度升高,氮杂有序介孔炭材料比表面积先增加而后降低,热处理时间的延长有利于比表面积增大,但升温速率对所制炭材料比表面积没有明显影响,当升温速率为30 oC/min,900 oC焙烧3 h时,氮杂有序介孔炭材料的比表面积达到最大值888 m2/g. XPS测试结果表明,随着热处理温度升高,氮杂有序介孔炭材料中含氮基团的分解进一步加深,使N含量逐渐降低.延长热处理时间亦然,而升温速率的改变对N含量无明显影响.在热处理温度较低时(600 oC),所得材料中N主要以吡咯氮和吡啶氮的形式存在;当温度达到800 oC以上,吡咯氮转化为吡啶氮和骨架氮,且主要以骨架氮形式存在,说明氮杂有序介孔炭材料的石墨化程度逐渐升高. Raman光谱结果显示,随着热处理温度升高, ID/IG逐渐降低,进一步印证了温度对石墨化程度的影响.
　　电化学测试结果表明,随着热处理温度升高,氮杂有序介孔炭材料的氧还原反应电催化活性逐渐升高,但是当热处理温度从900 oC升至1000 oC时,氧还原反应活性增加很小;升温速率与热处理时间对氧还原反应电催化活性的影响均不明显.与商品Pt/C催化剂相比,900 oC以上所制催化剂均表现出更优异的氧还原电催化活性与选择性.由此可见,热处理温度是决定碳源热化学行为的关键因素,进而决定炭材料表面组成与结构.电化学研究结果表明,800 oC以上进行热处理碳化,所生成石墨化微晶可有效促进电子传递,降低欧姆极化损失,同时,较高的处理温度可促进骨架氮掺杂,从而构建出高效氧还原反应活性位点.因此,氮杂型炭催化剂的组成、结构与电化学性能更多地受控于热处理过程中的热力学,而非热解动力学过程.     

Preparation of a kind of mesoporous carbon and its performance in adsorptive desulfurization

Carbon materials were prepared using mesoporous silica HMS with different pore sizes as the hard templates and water-soluble phenolic resin as the carbon source. The obtained materials were characterized by powder X-ray diffraction, transmission electron microscopy and N₂ physical adsorption, and were used in adsorptive desulfurization. It has been shown that the carbon material prepared using HMS with larger pore size (>3 nm) presented uniform wormlike mesopore of 2.3 nm and large BET surface area (1903 m²/g). The mesoporous carbon was an excellent adsorbent to remove the refractory sulfur compound in diesel, especially dibenzothiophene and 4, 6-dimethyldibenzothiophene.     

氮掺杂介孔炭负载FeCu双金属催化剂及其CO加氢性能研究

利用氮掺杂介孔炭负载FeCu双金属,改变Fe/Cu组成,考察催化剂结构性质特征及其CO加氢反应性能。结果表明,Fe、Cu与N相互作用存在差异,Cu-N相互作用较强,并直接促进了Cu的分散。在较高的金属负载量（45.0%-50.0%,质量分数）下,Cu仍保持了与N一致的均匀分布特征,催化剂表面Fe/Cu组成也因为Fe、Cu分布特征差异而小于体相,这与常见Fe-Cu体系明显不同。在所用预处理条件（300℃的H₂气氛）下,Fe未被完全还原,H主要与Fe-O作用,以Fe-O-H形式存在,而Cu-N作用较强,金属Cu与H作用较弱,使得催化剂表面活性氢碳比降低,导致C₅₊选择性随Fe/Cu比值的减小逐渐增加。与此同时,载体向负载金属的电子偏移能力也随着Fe/Cu比值的减小逐渐增强,促使催化剂表面碱性随Cu含量的增加逐渐增强,最终导致C₅₊选择性、醇选择性进一步增加。     

Different non-radical oxidation processes of persulfate and peroxymonosulfate activation by nitrogen-doped mesoporous carbon

Activated persulfate oxidation is an emerging advanced oxidation process for organic pollutant degradation. Own to different molecular structures and oxidation potentials, persulfate (PDS) and peroxymonosulfate (PMS) may show different degradation performances due to various catalytic mechanisms even by the same catalysts. In this study, the nitrogen-doped mesoporous carbon (N-OMC) was applied to activate PDS and PMS for degrading a model organic pollutant phenol to reveal their activation mechanisms. Results show that both PDS and PMS could be efficiently activated by N-OMC. The degradation of phenol fitted well with pseudo-first-order kinetics, whose kinetic constants increased with the increase of pH, PDS/PMS dosage, and N-OMC dosage. Based on quenching experiments and electron spin resonance spin-trapping technique, the N-OMC was found to activate PDS and PMS via non-radical process of electron transfer and singlet oxygen formation, respectively, instead of the commonly observed radical process. This work will be useful to understand the activation processes of PDS and PMS, and benefit for the development of catalysts for pollutant degradation.     

Templated synthesis of electroactive periodic mesoporous organosilica bridged with oligoaniline

The synthesis and characterization of novel electroactive periodic mesoporous organosilica (PMO) are reported. The silsesquioxane precursor, N,N'-bis(4'-(3-triethoxysilylpropylureido)phenyl)-1,4-quinonene-diimine (TSUPQD), was prepared from the emeraldine base of amino-capped aniline trimer (EBAT) using a one-step coupling reaction and was used as an organic silicon source in the co-condensation with tetraethyl orthosilicate (TEOS) in proper ratios. By means of a hydrothermal sol-gel approach with the cationic surfactant cetyltrimethyl-ammonium bromide (CTAB) as the structure-directing template and acetone as the co-solvent for the dissolution of TSUPQD, a series of novel MCM-41 type siliceous materials (TSU-PMOs) were successfully prepared under mild alkaline conditions. The resultant mesoporous organosilica were characterized by Fourier transform infrared (FT-IR) spectroscopy, thermogravimetry, X-ray diffraction, nitrogen sorption, and transmission electron microscopy (TEM) and showed that this series of TSU-PMOs exhibited hexagonally patterned mesostructures with pore diameters of 2.1-2.8 nm. Although the structural regularity and pore parameters gradually deteriorated with increasing loading of organic bridges, the electrochemical behavior of TSU-PMOs monitored by cyclic voltammetry demonstrated greater electroactivities for samples with higher concentration of the incorporated TSU units.