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以酚醛树脂作为碳源,采用嵌段共聚物模板法一步制备新型有序介孔碳化钨/碳(WC/C)纳米颗粒. WC/C颗粒的比表面积为414 m2·g-1,表面的平均孔径约为38 nm,处于介孔范围内(2 ~ 50 nm). 通过调节树脂预聚时间以及碳化温度等条件制备出结构形貌较优的WC/C复合材料,并探讨了材料形成机理. 使用X射线衍射、扫描电镜、透射电镜及氮气吸脱附等方法表征了复合材料的结构. 将贵金属铂负载于WC/C表面制备得新电催化材料Pt-WC/C,使用循环伏安法和计时电流法对Pt-WC/C复合材料的电化学性能进行检测,并与商用碳载铂(Pt/C)材料进行对比. 测试结果发现,Pt-WC/C对甲醇的电催化活性以及稳定性等方面都表现出优于商用Pt/C材料的活性,这主要归功于碳化钨高度分散于碳表面. 相似文献
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以低分子量的酚醛树脂为碳源, F127为模板剂, NiCl2为石墨化促进剂, 通过一步模板法辅助合成有序介孔碳. X射线衍射(XRD)、激光拉曼和透射电子显微镜(TEM)等测试结果表明, Ni以金属颗粒的方式进入碳材料的骨架中, 明显提高了有序介孔碳的石墨化程度, 而碳的有序介孔结构几乎没有变化. 在700 ℃热解温度下, Ni含量为5%时, 可以清晰地观察到Ni周围呈现碳的石墨结构. 在硫酸和甲醇溶液中进行循环伏安测试, 结果显示, 碳材料的石墨化有利于提高其电催化活性, 含Ni 5%的碳载Pt催化剂电化学活性面积可达24.84 m2•g-1, 甲醇氧化峰电流为3.92 mA. 相似文献
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有序介孔碳的合成及其相转变机理的研究 总被引:1,自引:0,他引:1
采用十六烷基三甲基溴化铵(CTAB)作为模板剂, 正硅酸乙酯(TEOS)为硅源, 在碱性条件下, 用低温合成方法合成了有序介孔硅, 并以此为硬模板, 蔗糖为碳前驱体, 采用液相浸渍方法填充碳源, 制备出有序介孔碳. 通过XRD、TEM、N2吸附-脱附等测试方法对其表征, 结果表明合成的介孔材料高度有序, 均具有很高的比表面积(介孔硅, 992~1096 m2/g; 介孔碳, 930~1208 m2/g), 较大的孔容和较窄的孔径分布. 还发现随着反应温度的升高, 介孔硅的结构从二维六方相(p6mm)转变为三维立方相(Ia3d); 介孔碳在复制介孔硅后, 其结构也从三维立方相(Ia3d)转变为四方相(I41/a), 并对相转变机理做了初步探讨. 相似文献
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有序介孔碳的微波快速合成和表面修饰及其负载性能 总被引:1,自引:0,他引:1
以低聚合度酚醛树脂为碳源、三嵌段共聚物F127(Mw=12600,PEO106PPO70PEO106)为模板导向剂,以微波辐照替代传统的烘箱热聚合,在常见功率下(400~800W)快速(15~60min)聚合,并高温碳化获得介孔碳。XRD、TEM、低温N2吸脱附等测试表明所得样品具有高度有序的介孔结构,比表面积和孔容分别可达614m2·g-1和0.47cm3·g-1。合成的介孔碳经NaBH4和胶体钯溶液两步修饰处理,表面被活化并沉积了Pd颗粒,导电性和亲水性均得到改善,载Pt的量和分散性明显提高,Pt/C催化剂的电化学活性面积由4m2·g-1增加到29m2·g-1。 相似文献
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以百里香酚蓝为前驱物,采用硬模版法一步合成硫掺杂的有序介孔碳材料(S-OMC)。在900℃下热解负载百里香酚蓝的介孔二氧化硅SBA-15,获得了具有石墨孔壁结构的有序介孔碳材料(S-OMC-900)。硫元素均匀有效地分布在碳材料介孔孔壁上,并对催化氧还原反应(ORR)起到了关键性作用。S掺杂的有序介孔碳材料的比表面积为1 230 m~2·g~(-1),孔径4.6 nm,有序的孔道结构保证了氧还原反应的物料运输,增大了催化活性。测试结果表明,所制备的S-OMC-900具有良好的催化活性和稳定性。与商业Pt/C比较,S-OMC-900具有更好的甲醇耐受性。 相似文献
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以二氧化硅溶胶为硬模板,嵌段聚合物F127为软模板,通过双模板法合成了高介孔比例、窄孔径分布的介孔碳(MC).进而经乙二醇还原法制备了高分散的MC载铂催化剂(Pt/MC).采用循环伏安、计时电流、线性扫描伏安和电化学阻抗谱法研究了硫酸溶液中乙二醇在Pt/MC催化剂电极上的电化学氧化行为.实验结果表明,Pt/MC催化剂对乙二醇的电催化氧化性能显著高于商业化炭黑XC72R载Pt(Pt/XC72R)催化剂.电化学阻抗谱分析进一步揭示,乙二醇在Pt/MC催化剂电极上的电氧化反应具有较低的电荷传递电阻.Pt/MC催化剂高的电催化活性可以归结于MC大的孔径和均一的介孔结构对电子传输和传质的促进作用. 相似文献
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An efficient approach to the synthesis of highly congested di, penta and hexacyclic pyrazoles as well as imidazole fragment containing novel heterocyclic molecule has been developed through a carbanion induced transformation of suitably functionalized 2H-pyran-2-ones, benzo[h]chromene and thiochromeno[4,3-b]pyrans. Due to the presence of fluorescence, we report their prime application metal sensor as off/on switching in ferric ions. 相似文献
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Uroš Grošelj Mojca Žorž Amalija Golobič Branko Stanovnik Jurij Svete 《Tetrahedron》2013,69(52):11092-11108
A new and simple synthesis of novel N-protected methyl 5-substituted-4-hydroxypyrrole-3-carboxylates, which exist in equilibrium with their 4-oxo tautomers, has been developed in two steps starting from N-protected α-amino acids. The key intermediates are enaminones, which can also be isolated, characterized, and used for the construction of other functionalized heterocycles, before they spontaneously decompose to pyrrole products. 4-Hydroxypyrroles are prone to partial aerial oxidation but can be efficiently alkylated or reduced to stable polysubstituted pyrrolidine derivatives. 相似文献
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The chemoselectivity in the intramolecular CH insertion of various diazosulfonamides has been experimentally studied. The results reveal that the aliphatic 1,4-, 1,5-, or 1,6-C(sp3)?H insertions of diazosulfonamides are not accessible, while the aromatic 1,5-C(sp2)?H insertion can be realized specifically by adjusting the diazo-adjacent group. In addition, the general chemoselectivities in the intramolecular CH insertions of diazosulfonyl compounds are summarized. Generally, diazosulfones undergo both aromatic 1,5-C(sp2)?H and aliphatic 1,5- and 1,6-C(sp3)?H insertions, while diazosulfonates undergo aliphatic 1,5- and 1,6-C(sp3)?H insertions. However, diazosulfonamides only undergo aromatic 1,5-C(sp2)?H insertion. 相似文献
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N-Heterocyclic carbene-palladacyclic complexes 3 were successfully achieved in a one-pot procedure under mild conditions. The structure of 3a was unambiguously confirmed by X-ray single crystal diffraction and it was an active catalyst in the Buchwald-Hartwig amination and α-arylation of ketones even at very low catalyst loadings (0.01?mol%). 相似文献
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An efficient tandem approach for the selective synthesis of 4,5-dihydroimidazo[1,5-a]quinoxalines 6a–g and imidazo[1,5-a]quinoxalines 7a–h by the reaction of 2-imidazolyl anilines 4a–c with aryl aldehydes 5a–k under mild reaction conditions is described. Introduction of electron releasing alkyl groups in substrates 4a–b was found to be instrumental for the success of the reaction. 相似文献
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The Diels-Alder reactivity of 1,2-heteroborines (H4C4B(H)X, X?=?NH, PH, AsH; O, S, Se) has been computationally explored by means of Density Functional Theory (DFT) calculations. The influence of the HB?=?X fragment on the reactivity of the system has been quantitatively analyzed in detail by means of the so-called Activation Strain Model (ASM) of reactivity. It is found that the interaction between these species and the dienophile is significantly stronger than that computed for their all-carbon isoelectronic counterpart, benzene. In addition, the strain energy plays a key role in the observed reactivity trends. The role of the aromaticity strength of these heteroarenes on the reactivity is also assessed. 相似文献
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Xi-Liu YunWen-Ying Bi Jian-Hui HuangYu Liu Daisy Zhang-NegrerieYun-Fei Du Kang Zhao 《Tetrahedron letters》2012,53(38):5076-5080
A variety of N-aryl and N-alkyl carbazolones were conveniently achieved in good to high yields via Pd2(dba)3-mediated intramolecular coupling of N-substituted α-iodo enaminones under microwave irradiation. The Pd(0)-catalyzed cyclization was found to proceed favorably with the more electron-deficient phenyl ring during the reactions involving unsymmetrical N,N-diaryl α-iodo enaminones. This unique property enables the construction of carbazolone skeleton containing nitro substituted benzenoid ring. 相似文献
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Shashikant U. Dighe Surya K. Samanta Shivalinga Kolle Sanjay Batra 《Tetrahedron》2017,73(17):2455-2467
An efficient iodine-mediated oxidative Pictet-Spengler reaction in dimethyl sulphoxide (DMSO) using terminal alkynes as the 2-oxoaldehyde surrogate for the synthesis of aryl (9H-pyrido[3,4-b]indol-1-yl)methanones is described. The scope of the protocol includes the total synthesis of Fascaplysin, Eudistomins Y1 and Y2. The methodology is extended for preparing pyrrolo[1,2-a]-quinoxaline and indolo[1,5-a]quinoxaline derivatives. The utility of 1-aroyl-β-carbolines was demonstrated by performing palladium-catalyzed β-carboline directed ortho-C(sp2)-H functionalization of the phenyl ring with thiomethyl (SMe) group using DMSO as source and for accessing 4-aryl-canthin-6-ones. 相似文献
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Both substituted 2,4,5,6-tetrahydrocyclopenta[c]pyrazoles and 2,4,5,6-tetrahydropyrrolo[3,4-c]pyrazoles have been synthesized by the 3+2 intramolecular dipolar cycloaddition of nitrilimines to alkynes. This cyclization has been extended to more versatile 3-bromo derivatives by the use of alkynylbromides as dipolarophiles. 相似文献
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In this Letter, we described a facile method for constructing fused bicyclic 1-arylpyrazol-5-one ring system. We employed various methylene-containing carboxylic acids as the substrates and proved that the pyrazolone ring closure requires activated methylene group in intermediate II. Accordingly, a series of structurally diversified, fused bicyclic 1-arylpyrazol-5-ones was prepared in moderate to high yields using the requisite substrates. 相似文献