高分散度Pt/C电催化剂的制备

Cabot公司Vulcan XC-72型炭黑，经过H2O2氧化处理后作为Pt的载体，H2PtCl6作为金属前驱体制备了高度分散的Pt/C催化剂。讨论了不同条件下H2PtCl6在炭黑上的吸附性能。载体经过H2O2氧化处理24h,H2PtCl6在pH=9下吸收48h，H2 350℃还原2h，可以制备出铂晶粒平均大小为1.8nm的Pt/C电催化剂。     

铁氮掺杂活性炭载体增强碳载铂基催化剂氧还原反应稳定性EI北大核心CSCD

修饰和改良载体是改善质子交换膜燃料电池阴极铂基催化剂性能的主要途径。以铁氮(FeN)掺杂活性炭(Black Pearl 2000,BP)为载体,获得负载型铂基催化剂。使用电化学方法对催化剂的氧还原反应活性以及稳定性进行测试,采用X射线衍射仪、比表面积和孔径分布测试、透射电子显微镜、X射线光电子能谱等分析手段对载体及催化剂结构进行表征。结果表明:Pt/FeN-BP催化剂与商业Pt/C催化剂的起始电位均为0.94 V,具有相当的氧还原反应初始活性;老化测试后,Pt/FeN-BP催化剂与商业Pt/C催化剂的起始电位损失分别约为10,30 mV,半波电位损失分别约为5,60 mV,Pt/FeN-BP催化剂的稳定性明显优于商业Pt/C催化剂。这是因为,铁氮掺杂碳载体具有适中的比表面积和孔径大小,Pt颗粒在载体上以小粒径的状态存在且老化测试后Pt颗粒无团聚现象,以及载体与Pt颗粒之间可能存在一定的相互作用。     

炭气凝胶负载Pt基催化剂的制备及其甲醇氧化催化性能

以间苯二酚(R)和甲醛(F)为原料,制备R-F炭气凝胶(RF-CAs).继以后者为载体采用浸渍还原法制备铂基催化剂Pt/CA,并比较其与由相同负载工艺制得的以Vulcan XC-72为载体的铂基催化剂Pt/XC72的催化甲醇氧化反应的性能.结果表明,前者具明显高的甲醇氧化催化活性,显示CAs是一种极具潜在竞争力的燃料电池催化剂载体材料.     

钯纳米颗粒在不同碳质材料上的自发沉积与电活性

在无还原剂存在下,氯化钯在Vulcan XC-72碳粉(C)、多壁碳纳米管(MWCNT)和碳球(CM)等碳质材料表面上自发还原为金属钯,从而得到相应的钯纳米颗粒(Pd-C、Pd-MWCNT和Pd-CM)。用阳离子表面活性剂十六烷基三甲基溴化铵(CTAB)对这些碳质材料修饰后,采用同样的自发还原方法分别制备出Pd/CTAB-C、Pd/CTAB-MWCNT和Pd/CTAB-CM催化剂。结果表明,CTAB修饰后的MWCNT明显增加了钯纳米颗粒的自发沉积量,粒径大约为9 nm,而在MWCNT上沉积的纳米Pd粒径为19 nm。Pd/CTAB-MWCNT在碱性条件下对乙醇氧化的电流密度达到44.2 m A·cm-2,与其他碳载体负载的Pd纳米催化剂相比,对乙醇氧化具有强而稳定的电催化活性。     

Pt/C催化剂制备及CO催化氧化性能研究

采用大气压介质阻挡放电辅助氢气热还原方法和氢气热还原方法制备Pt/C催化剂,考察了制备方法及Pt负载量对Pt/C催化性能的影响。采用X-射线衍射(XRD)、循环伏安法、CO催化氧化反应研究Pt/C催化剂的晶相结构、电催化性能和CO催化氧化活性。结果表明:大气压介质阻挡放电辅助氢气热还原所制备的样品具有更高的电化学活性和CO催化氧化活性。当Pt负载量在2%到10%之间变化时,Pt/C-PC催化活性随负载量增加而增加。XRD测试结果显示当Pt负载量为2%,5%和10%时,Pt粒径分别为:10.6 nm,9.1 nm和6.4 nm,说明采用等离子体辅助氢气热还原方法制备的Pt/C-PC催化剂,Pt负载量越大,Pt粒径越小,CO催化氧化活性更高。     

MOF(Co)/功能化石墨烯制备高效Co-N-C型氧还原催化剂研究

以六水合硝酸钴为金属源,苯并咪唑为有机配体,对苯二胺改性氧化石墨烯(PGO)为碳载体,采用一步溶剂热法合成金属有机骨架(MOF)-PGO前躯体,经过高温处理制备了多孔Co-N-PGO催化剂。采用比表面积孔隙度分析仪、扫描电子显微镜、透射电子显微镜、X射线衍射、拉曼光谱和X射线光电子能谱等物理表征手段对催化剂形貌、结构以及元素形态进行表征,同时利用线性扫描伏安法和计时电流法对催化剂在碱性电解液中的氧还原(ORR)性能进行测试。结果表明,Co-N-PGO催化剂具有较高的比表面积和电化学活性面积,良好的结晶程度以及丰富的孔洞结构。此外,Co-N-PGO催化剂表现出优异的ORR催化活性,半波电位与商业Pt/C催化剂相比仅相差10mV,同时拥有更好的稳定性及抗甲醇毒化性能。根据K-L方程,Co-N-PGO催化剂在ORR过程中主要为四电子途径,与Pt/C催化剂反应机理相似。     

Co修饰的碳载Pt纳米粒子催化剂的制备与表征

质子交换膜燃料电池阴极需要使用高活性的电催化剂来加速氧还原反应(ORR)速率,而提高活性成分贵金属铂(Pt)的功能反应利用率可解决其关键问题.本工作利用过渡金属钴Co(Ⅱ)?有机框架(Co?MOF)为前驱体合成ORR催化剂载体Co/C,并采取浸渍?液相还原法负载Pt纳米粒子制备了合金Pt?Co/C催化剂.通过对样品的孔隙结构、物相结构、微观形貌等表征,证实了载体Co/C具有较大的比表面积和相互连通的分级介孔结构,其独特的形貌、丰富的孔隙结构使负载的Pt纳米颗粒均匀分布、粒径范围窄,平均粒径约为6.8 nm.进一步对催化剂进行电化学性能评价,其电化学活性表面积(ECSA)接近于商用Pt/C催化剂的值,结果表明合金催化剂中活性成分Pt具有较高的利用率,同时还表现出载体独特的孔隙结构优势.     

碳负载尺寸可控的铂纳米粒子微波合成和表征

分别以XC-72碳和碳纳米管为载体,H₂PtCl₆为前驱体,用微波辐射加热的方法合成了碳负载的铂纳米粒子,并对其进行了EDX、TEM和XRD表征.研究了H₂PtCl₆乙二醇溶液的pH值对微波合成铂纳米粒子的大小、均匀性及其在碳载体上分散程度的影响.研究结果发现对于Pt/XC-72碳,随着pH值从3.4增加到9.5,铂纳米粒子的平均粒径从5.5nm减小到2.7nm;对于Pt/CNTs,随着pH值从3.5增加到9.4,铂纳米粒子的平均粒径从5.3nm减小到2.8nm.另外,随着pH值的增加,铂纳米粒子的尺寸均匀性及其在碳载体表面的分散程度得到改善.     

基于金属-有机框架的M-N/C类催化剂在氧还原反应中的应用

燃料电池阴极发生氧还原反应(ORR)的动力学过程缓慢，通常需要Pt/C作为催化剂降低反应过电位。然而Pt作为一种贵金属，其使用将极大增加燃料电池的生产成本，因此开发非贵金属催化剂来替代Pt/C催化剂具有重要意义。金属有机框架材料(MOFs)因其具有高比表面积、有序多孔结构、拓扑结构可调等特点作为前驱体被广泛应用于M-N/C类催化剂的合成。M-N/C类催化剂继承了MOFs的结构特征，且具有丰富的活性位点，提高催化活性和分级结构以促进传质过程，因此表现出良好的ORR催化性能。从单金属/氮/碳和多金属/氮/碳组成角度出发，对近几年来关于M-N/C类催化剂的结构设计思路和合成策略进行了总结，阐述了其在ORR中的催化性能，展望了其未来发展前景。     

氢气还原法制备Pt/MoOx/C及其对氧还原的电催化性能

用氢气在高温下还原吸附到碳载体上的钼酸铵和氟铂酸,制备出Pt/MoOx/C金属-氧化物复合型催化剂.考察了Pt/MoOx/C催化剂的电化学性能,经旋转圆盘电极测试表明在低电位区Pt/MoOx/C对含甲醇溶液中的氧还原的催化活性高于Pt/C.     

Stabilization of embedded Pt nanoparticles in the novel nanostructure carbon materials

An extremely durable and highly active Pt catalyst has been successfully prepared by embedding Pt(0) nanoparticles inside the pores of the nitrogen-dotted porous carbon layer surrounding carbon nanotubes (Pt@NC-CNT). The Pt@NC-CNT catalyst has a high BET surface area of 271 m(2) g(-1) (62 m(2) g(-1) for Pt/XC-72) and comparably high electrochemically active surface area of 64.3 m(2) g(-1) (68.2 m(2) g(-1) for Pt/XC-72). The prepared Pt nanoparticles are small in size (2.8 ± 1.3 nm) and have a strong interaction of nitrogen to platinum, as evidenced by the binding energy observed at 399.5 eV. The maximum current densities (I(f)) during methanol oxidation observed for Pt@NC-CNT (13.2 mA cm(-1)) is 1.2 times higher than that of Pt/XC-72 (10.8 mA cm(-1)) catalysts. Remarkably, in the long term durability test, the I(f) after 1000 cycles for Pt@NC-CNT decreased to 10.6 mA cm(-1) compared with Pt/XC-72, which decreased to 2.6 mA cm(-2). This means that the Pt@NC-CNT catalyst has a tremendously stable electrocatalytic activity for MOR because of the unique structure of Pt@NC-CNT formed in this novel synthesis technique.     

Preparation and catalytic activity of Pt/C materials via microwave irradiation

Microwave heating was employed to prepare highly dispersed Pt/C catalyst. Uniform platinum nanoparticles with average diameter of about 3.0-5.0 nm dispersed on carbon materials (XC-72) were synthesized using a domestic microwave oven. Synthesized Pt/C materials were characterized by X-ray diffraction and transmission electron microscopy. The particle size and size distribution of Pt nanoparticles greatly depend on microwave irradiation duration, where the heating temperature rises rapidly as the process proceeds. Cyclic voltammetry demonstrates that Pt/C catalysts derived from microwave irradiation for 90 s exhibits higher catalytic activity than a commercial Pt/C catalyst (E-Tek) at room temperature. The improvement in electrocatalytic activity of synthesized Pt/C materials is attributed to uniformity of particle size, well dispersion and high surface area, which is obtained around 175 °C and irradiation for 90 s.     

载体表面化学状态对Pt/C催化剂结构及电催化活性的影响

对碳黑进行不同条件的氧化处理得到不同表面化学状态的载体,以甲醛为还原剂,氯铂酸为前驱体,制备Pt/C电催化剂.运用X射线光电子能谱(XPS)、X射线衍射(XRD)、透射电镜(TEM)等分析手段研究碳黑及Pt/C催化剂的化学组成、化学状态、晶体结构及表面形貌,并用循环伏安法(CV)测试Pt/C催化剂对甲醇的电催化氧化.结...     

Preparation and characterization of PtRu nanoparticles supported on nitrogen-doped porous carbon for electrooxidation of methanol

N-doped porous carbon nanospheres (PCNs) were prepared by chemical activation of nonporous carbon nanospheres (CNs), which were obtained via carbonization of polypyrrole nanospheres (PNs). The catalysts, PtRu and Pt nanoparticles supported on PCNs and Vulcan XC-72 carbon black, were prepared by ethylene glycol chemical reduction. Transmission electron microscopy, X-ray diffraction, and energy-dispersive X-ray spectroscopy were employed to characterize samples. It was found that PCNs containing N function groups possess a large number of micropores. Uniform and well-dispersed Pt and PtRu particles with narrow particle size distribution were observed. The electrooxidation of liquid methanol on these catalysts was investigated at room temperature by cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy (EIS). The results showed that alloy catalyst (Pt(1)Ru(1)/PCN) possessed the highest catalytic activity and better CO tolerance than the other PtRu and Pt-only catalysts; PtRu nanoparticles supported on PCN showed a higher catalytic activity and more stable sustained current than on carbon black XC-72. Compared to commercial Alfa Aesar PtRu catalyst, Pt(1)Ru(1)/PCN reveals an enhanced and durable catalytic activity in methanol oxidation because of the high dispersion of small PtRu nanoparticles and the presence of N species of support PCNs.     

PEMFC膜电极电催化层的制备和性能

膜电极催化层的组成和电催化剂的活性对质子交换膜燃料电池的性能有很大影响．采用浸渍还原法制备出了Pt平均粒径为3．1nm的Pt／C催化剂．催化剂中Pt的粒径和在碳黑载体（VulcanXC-72）表面的分散程度采用透射电镜（TEM）进行测试．用Pt／C催化剂、适量的Nation溶液和PrFE乳液制备出质子交换膜燃料电池（PEMFc）膜电极的催化剂层,并研究了该催化剂层中PTFE含量对其性能的影响．实验表明,PTFE强烈的疏水性可以迫使部分水分向阳极反扩散,催化层中加入适量的PTFE可以使膜电极具有一定的水管理能力,在去掉辅助增湿系统的条件下具有良好的极化性能．     

Pt/MWNTs催化剂的制备及其性能

以多壁碳纳米管为载体，用液相还原法制备了Pt／MWNTs催化剂，通过XRD、TEM等技术对催化剂进行了表征，并将所制催化剂组装成燃料电池，以H2、O2为反应气，测试了催化剂的性能，结果显示Pt／MWNTs催化剂具有优良的电催化活性。     

载体炭与Pt催化剂之间的相互作用及其引起的尺寸效应(英文)

通过乙二醇还原,在VulcanXC-72炭黑上负载了三种具有不同平均粒径(1.7nm,3.0nm和5.0nm)的Pt催化剂。利用透射电子显微镜,研究了载体炭黑表面的微孔与Pt催化剂之间的几何相互作用。结果表明:尺寸较小的Pt颗粒(平均粒径为1.7nm)通常被包含在载体表面的微孔中,表现为被一薄碳层所覆盖并嵌入炭黑基体。而尺寸较大的Pt颗粒(平均粒径为3.0nm和5.0nm)则不存在这种现象,往往显示出裸露的清洁表面。这种与载体表面微孔的不同相互作用引起了Pt颗粒在电化学活性比表面上的反常尺寸效应,进而影响了其催化甲醇氧化的质量比活性。     

Temperature dependence of graphene oxide reduced by hydrazine hydrate

Graphene oxide (GO) was successfully prepared by a modified Hummer's method. The reduction effect and mechanism of the as-prepared GO reduced with hydrazine hydrate at different temperatures and time were characterized by x-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), elemental analysis (EA), x-ray diffractions (XRD), Raman spectroscopy and thermo-gravimetric analysis (TGA). The results showed that the reduction effect of GO mainly depended on treatment temperature instead of treatment time. Desirable reduction of GO can only be obtained at high treatment temperature. Reduced at 95?°C for 3 h, the C/O atomic ratio of GO increased from 3.1 to 15.1, which was impossible to obtain at low temperatures, such as 80, 60 or 15?°C, even for longer reduction time. XPS, 13C NMR and FTIR results show that most of the epoxide groups bonded to graphite during the oxidation were removed from GO and form the sp(2) structure after being reduced by hydrazine hydrate at high temperature (>60?°C), leading to the electric conductivity of GO increasing from 1.5 × 10(-6) to 5 S cm(-1), while the hydroxyls on the surface of GO were not removed by hydrazine hydrate even at high temperature. Additionally, the FTIR, XRD and Raman spectrum indicate that the GO reduced by hydrazine hydrate can not be entirely restored to the pristine graphite structures. XPS and FTIR data also suggest that carbonyl and carboxyl groups can be reduced by hydrazine hydrate and possibly form hydrazone, but not a C = C structure.     

Catalytic performance of acid-treated multi-walled carbon nanotube-supported platinum catalyst for PEM fuel cells

Effects of the surface functional groups of multi-walled carbon nanotubes (MWCNTs) as catalyst support for the durability of polymer electrolyte membrane fuel cells (PEMFCs) were examined at high Pt loading conditions. The amount of oxygen functional groups on the MWCNTs surface was increased as the acid treatment time and temperature increased. We found that more functional groups in MWCNTs improved initial Pt dispersion but deteriorated durability due to the reduced carbon corrosion resistance. The experimental results also showed that despite the surface oxidation, Pt/MWCNT catalysts showed highly improved durability than Pt/C catalysts due to the graphitic nature of MWCNTs. Membrane electrode assembly (MEA) fabricated by 4 h acid treated MWCNTs at 25 °C showed 4 times better durability than commercial Pt/C based MEA at the reverse potential operation generated by fuel starvation conditions. We believe that MWCNTs can be effectively used for PEMFCs even at high loading due to their excellent anti-corrosion properties.