共查询到19条相似文献,搜索用时 171 毫秒
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以椰壳活性炭为载体,乙二醇为还原剂,超声辅助还原法制备了钯碳催化剂(Pd/C-u)。利用N2物理吸附、X射线衍射分析(XRD)、透射电子显微镜(TEM)等对所制备的Pd/C催化剂进行了结构与形貌的表征,结果表明,钯纳米粒子为面心立方结构,均匀地分布在活性炭表面,平均粒径为6.16nm。当以超声辅助还原法制备Pd/C为催化剂进行对溴甲苯和对溴硝基苯与苯硼酸的Suzuki偶联反应时,在0.1%催化剂用量,60℃下反应30min时,反应收率分别为98.22%和82.08%,高于常规还原法制备的Pd/C-c催化剂。 相似文献
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《化学工业与工程技术》2019,(2):33-37
采用浸渍法制备了Pd/C催化剂,考察了催化剂制备过程中加料方式、还原方法、载体种类、钯质量分数和浸渍液质量浓度对催化剂性能的影响,得到了制备Pd/C催化剂的优化工艺条件:载体为NH-03型活性炭,浸渍液质量浓度为20 g/L,采用滴加的方式将PdCl_2溶液加至活性炭浆液中,还原剂为(w)20%的次亚磷酸钠溶液,钯质量分数为5%。优化制备条件下制得的Pd/C催化剂用于催化加氢制备4-氨基二苯胺,表现出较好的活性,其中4-硝基二苯胺和4-亚硝基二苯胺转化率均可达到100%,4-氨基二苯胺选择性大于99%,加氢反应时间小于30 min。催化剂SEM表征结果表明:自制的Pd/C催化剂表面活性炭载体凸起部分与Pd粒子粒径相当,有利于Pd粒子在活性炭表面的负载,提高Pd粒子的吸附牢固度和分散性,进而提高了Pd/C催化剂的活性。 相似文献
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以不同浓度的KMnO4溶液预处理的炭黑为载体,通过沉淀共还原法合成了3种Pd1Ni1/ACx (x=3,5,7)催化剂,并将3种催化剂与商业Pd/C催化剂进行了性能对比。用XPS、ICP、XRD和TEM对催化剂了进行表征。结果表明:Pd1Ni1/AC5的Pd负载量(质量分数,下同)最大(3.66%),Pd晶粒的平均粒径最小(4.71 nm),且均匀地分布在KMnO4氧化处理后的碳载体上,活性位点较多;XRD显示,3种Pd1Ni1/ACx催化剂中的Ni均以无定形存在。在电化学性能测试中,3种催化剂均表现出比商业Pd/C更好的电化学稳定性和存活率;其中,Pd1Ni1/AC5电化学活性表面积达62.21 m2/gPd,且乙醇催化活性为1797.85 A/gPd。 相似文献
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以Hollandite型氧化物Pb_(2-x)Mn_8O_(16)为载体,Na BH4、甲醛和乙二醇为还原剂,采用液相沉积还原法制备了3种载Pd催化剂,并利用X射线衍射(XRD)、透射电子显微镜(TEM)、X射线光电子能谱(XPS)等技术对催化剂进行表征,分析了不同还原剂对催化剂微观结构、氧化还原性质及其在苯酚氧化羰基化反应中催化性能的影响。实验结果表明,Na BH4的强还原性破坏了载体Pb_(2-x)Mn_8O_(16)的结构;与甲醛相比,以乙二醇为还原剂所得的纳米钯粒子在载体上的分布更加均匀,Pd粒子的平均尺寸为4.1 nm。其中采用乙二醇为还原剂制备的Pd/Pb_(2-x)Mn_8O_(16)催化合成碳酸二苯酯的收率最高,达15.6%。 相似文献
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以无花果(FL)树叶提取液作为还原剂、稳定剂,以树叶残渣(RFL)为载体,制备了负载型纳米钯铜合金催化剂(Pd Cu/RFL)。采用XRD、FT-IR、TEM、XPS、N2-吸附脱附等手段对制备的Pd Cu/RFL催化剂进行了表征,并研究了其催化Suzuki偶联反应的性能。Pd4Cu1NPs的粒径分布在2.31~6.62nm之间,平均粒径为3.97nm,均匀地分散在载体RFL表面。Pd与Cu间的电子转移和Pd4Cu1NPs与载体表面上含氧含氮官能团的络合不仅提高了Pd Cu/RFL催化Suzuki偶联反应活性,也改善了催化剂的稳定性。当Pd的加入量为反应底物的0.06mol%时,催化对溴硝基苯和苯硼酸的反应收率可以达到97.00%,催化剂重复使用9次后,收率仍可以保持在93%以上。 相似文献
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The high‐quality carbon supported Pd nanoparticles (Pd/C) composites have wide applications in catalysis. In this work, we demonstrate an efficient diethylene glycol (DEG) reduction method for the synthesis of a Pd/C catalyst with high dispersion and small particle size. During the synthesis, no surfactants and halogen ions are introduced in the reaction system, and DEG efficiently acts as solvent and reducing agent, which results in a “clean” Pd surface. Meanwhile, compared to the classic ethylene glycol (EG) reduction method, the present DEG reduction method can produce the high‐quality Pd/C composites. As a result, the as‐prepared Pd/C electrocatalyst exhibits a large electrochemical active surface area and good electrocatalytic performance for the methanol oxidation reaction in an alkaline media, due to the high dispersion and small particle size. This result indicates the as‐prepared Pd/C electrocatalyst has potential applications in alkaline direct methanol fuel cells. 相似文献
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A new carbon-supported PdNi (PdNi/C) catalyst is prepared by a simple simultaneous reduction reaction with sodium borohydride
in glycol solution. The results show that the performance of PdNi/C catalyst for formic acid oxidation is greatly improved
compared with that of Pd/C. X-ray diffraction (XRD) results show that Ni exists in the catalyst both as NiO and as PdNi alloy.
The value of the apparent activation energy shows that the activity of formic acid oxidation on the PdNi/C is more sensitive
to temperature compared with Pd/C. 相似文献
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Size-controlled synthesis and impedance-based mechanistic understanding of Pd/C nanoparticles for formic acid oxidation 总被引:1,自引:0,他引:1
This work provides a detailed electrochemical impedance study for formic acid electro-oxidation on size-controlled Pd/C nanoparticles, the synthesis of which was done by a simple protocol using ethylene glycol as a reducing agent. By controlling KOH concentration, this strategy provides a synthesis method for Pd nanoparticles with a selective size range of 3.9–7.5 nm. The as-prepared Pd nanoparticles exhibited size-dependent electrochemical property and electrochemical characterizations of four different Pd/C nanocatalysts (3.9, 5.2, 6.1, and 7.5 nm) showed that Pd particle with average size of 6.1 nm has the highest formic acid oxidation activity. Electrochemical impedance-based characterizations of formic acid oxidation on Pd/C suggested that at high potentials the adsorbed oxygen species could block the catalyst surface and inhibit the oxidation reaction, as reflected by the negative polarization resistance. Unlike Pd/C, the intermediate adsorbed CO species (COads) plays a critical role for formic oxidation on Pt/C and thus the impedance spectra of Pd/C and Pt/C appear different potential-dependent patterns in the second quadrant. The issue of CO was investigated by an impedance investigation of Pd/C in a mixture of formic acid containing dissolved CO. 相似文献
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Guiyan Yu Weixiang Chen Jie Zhao Qiulin Nie 《Journal of Applied Electrochemistry》2006,36(9):1021-1025
Pt/C electrocatalysts were prepared from a solution of H2PtCl6 in ethylene glycol in the presence of XC-72 carbon by adding a small amount of sodium acetate as stabilizer. Repeated TEM images showed that the platinum nanoparticles were small and uniform in size and highly dispersed on XC-72 carbon supports when a small amount of sodium acetate solution was added to the synthesis solution. The Pt/C electrocatalysts exhibited very high electrocatalytic activity for liquid methanol oxidation. The effects of adding acetate on Pt particle size and size distribution are discussed. It is demonstrated that acetate can be used as a good stabilizer for preparing Pt/C catalyst with fine and uniform Pt particles. 相似文献
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S. Yongprapat A. Therdthianwong S. Therdthianwong 《Journal of Applied Electrochemistry》2012,42(7):483-490
An Au/C catalyst was prepared by means of the polyvinyl alcohol-protected Au sol method. Highly dispersed Au nanoparticles
with an average particle size of around 3.7 nm were obtained as confirmed by transmission electron microscopy. The cyclic
voltammogram of Au/C was similar to that of a bulk Au electrode, but a small shift of Au oxide reduction and oxidation potential
peaks were observed. The electrooxidation of methanol, ethanol, ethylene glycol, and glycerol on the Au/C catalyst in an alkaline
solution was analyzed. Using a cyclic voltammogram, the maximum current density toward alcohol electrooxidation was found
to decrease in the order of glycerol > ethylene glycol > ethanol, while methanol was not oxidized. Compared with PtRu/C, the
maximum current densities obtained from the Au/C catalyst for ethylene glycol and glycerol electrooxidation were increased
by 1.6 and 3.3 times, respectively. The reaction heavily progressed through a C–C bond dissociation path. It was found that
main product of glycerol electrooxidation was formic acid, which accounted for more than 60 % of the total product. Using
chronoamperometry, the Au/C catalyst showed much better stability than that of PtRu/C for the reaction without C–C bond dissociation
and better stability for the reaction with C–C bond dissociation. 相似文献
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G. F. Alvarez M. Mamlouk S. M. Senthil Kumar K. Scott 《Journal of Applied Electrochemistry》2011,41(8):925-937
Pd nanoparticles have been synthesised using different reducing agents, including ethylene glycol (EG), formaldehyde and sodium borohydride and their activity for the oxygen reduction reaction (ORR) evaluated. The use of EG led to the best morphology for the ORR and this synthetic method was optimised by adjusting the system pH. Carbon-supported Pd nanoparticles of approximately 7 nm diameter were obtained when reduction took place in the alkaline region. Pd synthesised by EG reduction at pH 11 presented the highest mass activity 20 A g?2 and active surface area 15 m2 g?1. These synthetic conditions were used in further synthesis. The effect of heat treatment in H2 atmosphere was also studied; and increased size of the palladium nanoparticles was observed in every case. The Pd/C catalyst synthesised by reduction with EG at pH 11 was tested in a low temperature H2/O2 (air) PEMFC with a Nafion® 112 membrane, at 20 and 40 °C. Current densities at 0.5 V, with O2 fed to the cathode, at 40 °C were 1.40 A cm?2 and peak power densities 0.79 W cm?2, approximately; which compared with 1.74 A cm?2 and 0.91 W cm?2, respectively for a commercial Pt/C. 相似文献
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Carbon cryogel as support of platinum nano-sized electrocatalyst for the hydrogen oxidation reaction
The kinetics of hydrogen oxidation reaction was studied in perchloric acid solution on carbon-supported Pt nanoparticles using the rotating disk electrode technique. Carbon cryogel and commercial carbon black. Vulcan XC-72 were used as catalyst supports. Pt/C catalysts were prepared by a modified polyol synthesis method in an ethylene glycol (EG) solution. Considerable effect has been observed for the specific surface area of carbon support on the fundamental properties of Pt/C catalyst, such as catalyst particle size distribution and dispersion as well as catalytic activity for the oxidation of hydrogen. X-ray diffraction (XRD) and transmission electron microscopy (TEM) images show that the particle size of the catalyst decreases with the increase of specific surface area of carbon support. Cyclic voltammetry (CV) was used for determination of the actual exposed surface area of catalyst particles. It was found that Pt catalyst prepared by using the novel carbon material displayed better hydrogen electrochemical oxidation activity than the catalyst prepared by using Vulcan XC-72. 相似文献