基于Pt/CNTs催化剂的燃料电池Pt/Buckypaper催化层的制备与表征

为了提高质子交换膜燃料电池催化剂中贵金属的利用率,以碳纳米管(CNTs)负载Pt为催化剂,设计制备了具有催化剂梯度分布结构的Pt/buckypaper催化层。利用扫描电子显微镜等多种表征手段,观察与分析了催化剂和催化层的结构及Pt含量分布,并考察了它们的电化学性能。结果表明,Pt/CNTs催化剂中Pt颗粒在超声混酸氧化处理过的CNTs表面上分布均匀,平均直径为2.4nm。其电化学活性表面积(ECSA)接近于商用Pt/C催化剂的值,比质量活性(MA)则远高于商用催化剂,且具备更为优异的电化学循环稳定性。利用这种催化剂制备的Pt/buckypaper催化层保持着较大的ECSA,表明其中的Pt颗粒具有较高的利用率,体现了这种新颖结构的独特优势。     

质子交换膜燃料电池中Pt/C及Pt合金/C催化剂的衰退机制研究综述

成本和耐久性依然是制约质子交换膜燃料电池商业化发展的两大瓶颈。首先综述了质子交换膜燃料电池阴极Pt/C催化剂在实际工作条件下的降解情况,并给出了可能的降解机制。结果表明,Pt/C催化剂在实际工作条件下,尤其是在汽车应用中是不稳定的,通常无法用作燃料电池阴极催化剂。而Pt合金催化剂因具有优异的氧还原催化性能和相对较好的耐久性,被认为有望解决成本和耐久性这两大难题,因此在质子交换膜燃料电池中日益得到重视和应用。但如何改善合金催化剂的耐久性依然是一个棘手的问题,文章最后详细综述了PtxCoy合金催化剂可能的衰退机理,以及可在一定程度上提高Pt合金催化剂耐久性的Pt单层结构和Pt核壳结构,这对催化剂的合成和设计具有一定的指导意义。     

主链结构对阴离子交换膜碱稳定性的影响

碱性阴离子交换膜燃料电池(AAEMFCs)可使用低成本的非Pt催化剂,具有反应高效及环境友好等优点,因可在一定程度上取代质子交换膜燃料电池(PEMFCs)而备受关注.阴离子交换膜(AEMs)作为AAEMFCs的核心部件,需要兼备优异的OH-传输性能、机械性能、热稳定性及碱稳定性等.但目前AEMs仍面临的巨大挑战是耐碱性...     

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．     

质子交换膜燃料电池膜电极的结构优化

膜电极(membrane electrode assembly,MEA)是质子交换膜燃料电池(proton exchange membrane fuel cell,PEMFC)的核心部件,为PEMFC提供了多相物质传递的微通道和电化学反应场所。为了实现燃料电池商业化目标,需要制备高功率密度、低Pt载量、耐久性好的MEA。在MEA中除了催化剂以外,各功能层结构、层与层之间的界面都对MEA的性能具有重要影响。传统方法(CCS法和CCM法)制备的MEA在结构上有很多缺陷,明显制约了Pt的利用率和系统传质能力。通过优化各功能层结构消除缺陷,将有利于进一步提升PEMFC综合性能。本文从传统MEA结构存在的问题出发,梳理了近年来关于催化层、质子交换膜和气体扩散层结构优化方面的文献,归纳总结了各先进结构的制备方法、构效关系以及优缺点,对未来高性能、低成本和长寿命的MEA的开发具有指导意义。     

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.     

质子交换膜燃料电池Pt/C阴极催化剂性能的强化研究评述

Pt/C是质子交换膜燃料电池普遍采用的电催化剂,但由于电池阴极氧还原的过电位较大,因此,必须进一步提高铂电催化剂的性能以降低燃料电池成本和改善电池电压输出性能,综述了提高Pt/C催化剂电催化性能的途径及其研究状况.     

聚合物质子传导电解质膜的研究进展

聚合物质子传导电解质膜(或称质子交换膜)作为质子交换膜燃料电池(PEMFC)的电解质和隔膜,其性能在很大程度上决定了PEMFC的性能.本文对目前已商业化的全氟磺酸膜和部分氟化膜以及目前正在大力开发的非氟化质子交换膜的状况及研究进展进行了介绍,并讨论了这些质子交换膜的结构、制备、性能以及它们在燃料电池中的应用.     

基于PBI的高温质子交换膜研究进展

提高质子交换膜燃料电池(PEMFC)的工作温度,不但可以解决催化剂易受CO毒化、水热管理复杂等问题,还可以提高质子交换膜燃料电池的能量转化效率,是当今燃料电池发展的主要方向。在众多高温质子交换膜材料中磷酸掺杂的聚苯并咪唑(PBI)膜最具发展前景。综述了PBI基高温质子交换膜的发展状况,对比分析了不同PBI基质子交换膜的性能,展望了PBI基质子交换膜的发展前景。     

新型碳材料质子交换膜燃料电池Pt催化剂载体的研究进展

质子交换膜燃料电池(PEMFC)具有能量转换效率高、功率密度大、室温启动快、噪音低和零污染等特点,有望减少二氧化碳排放量,缓解能源危机,在轨道交通、航空航天等领域具有广阔的应用前景。催化剂是PEMFC的关键材料, Pt催化氧还原反应活性和稳定性好,是广泛使用且很难被取代的电催化剂。然而Pt储量低、价格昂贵,导致PEMFC成本较高,使用Pt载体可减少PEMFC的Pt负载量,提高Pt利用率。碳材料具有成本低廉、比表面积大、孔结构丰富、电导率和表面性质可调等特性,是广泛应用的Pt载体。商用的炭黑载体对Pt的利用效率低,抗电化学腐蚀性较差。为了进一步提高PEMFC的性能和持续性,需要研发能够均匀负载Pt、高效利用Pt、抗电化学腐蚀性强且导电性好的碳载体,进而实现PEMFC的大规模应用。炭气凝胶、碳纳米管和石墨烯等新型碳载体具有独特的结构和性质,可以提高PEMFC性能和寿命,引起了研究者的广泛关注。本文对近年来PEMFC新型碳材料Pt载体的研究进展进行了较为详细的综述,并对其发展趋势作出了适当评论。     

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.     

Pt‐Based Nanocrystal for Electrocatalytic Oxygen Reduction

Currently, Pt‐based electrocatalysts are adopted in the practical proton exchange membrane fuel cell (PEMFC), which converts the energy stored in hydrogen and oxygen into electrical power. However, the broad implementation of the PEMFC, like replacing the internal combustion engine in the present automobile fleet, sets a requirement for less Pt loading compared to current devices. In principle, the requirement needs the Pt‐based catalyst to be more active and stable. Two main strategies, engineering of the electronic (d‐band) structure (including controlling surface facet, tuning surface composition, and engineering surface strain) and optimizing the reactant adsorption sites are discussed and categorized based on the fundamental working principle. In addition, general routes for improving the electrochemical surface area, which improves activity normalized by the unit mass of precious group metal/platinum group metal, and stability of the electrocatalyst are also discussed. Furthermore, the recent progress of full fuel cell tests of novel electrocatalysts is summarized. It is suggested that a better understanding of the reactant/intermediate adsorption, electron transfer, and desorption occurring at the electrolyte–electrode interface is necessary to fully comprehend these electrified surface reactions, and standardized membrane electrode assembly (MEA) testing protocols should be practiced, and data with full parameters detailed, for reliable evaluation of catalyst functions in devices.     

Fuel Cell Electrocatalyst Using Polybenzimidazole‐Modified Carbon Nanotubes As Support Materials

Toward the next generation fuel cell systems, the development of a novel electrocatalyst for the polymer electrolyte fuel cell (PEFC) is crucial to overcome the drawbacks of the present electrocatalyst. As a conductive supporting material for the catalyst, carbon nanotubes (CNTs) have emerged as a promising candidate, and many attempts have been carried out to introduce CNT, in place of carbon black. On the other hand, as a polymer electrolyte, polybenzimidazoles (PBIs) have been recognized as a powerful candidate due to the high proton conductivity above 100 °C under non‐humid conditions. In 2008, we found that these two materials have a strong physical interaction and form a stable hybrid material, in which the PBIs uniformly wrap the surfaces of the CNTs. Furthermore, PBIs serve as effective binding sites for the formation of platinum (Pt) nanoparticles to fabricate a ternary composite (CNT/PBIs/Pt). In this review article, we summarize the fundamental properties of the CNT/PBIs/Pt and discuss their potential as a new electrocatalyst for the PEFC in comparison with the conventional ones. Furthermore, potential applications of CNT/PBIs including use of the materials for oxygen reduction catalysts and reinforcement of PBI films are summarized.     

An electrochemical impedance spectroscopy study of polymer electrolyte membrane fuel cells electrocatalyst single wall carbon nanohorns-supported

Electrochemical impedance spectroscopy (EIS) was used to study the polymer electrolyte membrane fuel cells (PEMFC) performance when using single wall carbon nanohorns (SWNH) to support Pt nanoparticles. Additionally, as-prepared and oxidized SWNH Pt-supports were compared with conventional carbon black. Two different oxidizing treatments were considered: oxygen flow at 500 degrees C and reflux in an acid solution at 85 degrees C. Both oxidizing treatments increased SWNH surface area; oxygen treatment increased surface area 4 times while acid treatment increased 2.6 times. The increase in surface area should be related to the opening access to the inner tube of SWNH. Acid treatment of SWNH increased chemical fragility and decreased electrocatalyst load in comparison with as-prepared SWNH. On the other hand, the oxygen treated SWNH sample allowed to obtain the highest electrocatalyst load. The use of as-prepared and oxygen treated SWNH showed in both cases catalytic activities 60% higher than using conventional carbon black as electrocatalyst support in PEMFC. Moreover, EIS analysis indicated that the major improvement in performance is related to the cathode kinetics in the as-prepared SWNH sample, while concerning the oxidized SWNH sample, the improvements are related to the electrokinetics in both anode and cathode electrodes. These improvements should be related with differences in the hydrophobic character between SWNH and carbon black.     

Fast and facile preparation of reduced graphene oxide supported Pt–Co electrocatalyst for methanol oxidation

In this study, we report a scalable, fast, and facile method for preparation of reduced graphene oxide (RGO) sheets supported Pt–Co electrocatalyst for methanol oxidation. Mixed reducing agents were used and the activity of the catalysts was studied. It was found that the presence of RGO leads to higher activity, which might be due to the increasing of electrochemically accessible surface areas and easier charge–transfer at the interfaces. Co can greatly enhance the electrocatalytic activity and moderate the poisoning of Pt catalyst. Under same Pt loading mass and experimental conditions, the RGO-Pt-Co catalyst shows the highest electro catalytic activity and improved resistance to carbon monoxide poisoning among the prepared catalysts.     

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.     

B或N掺杂端部封闭碳纳米管吸附Pt的第一性原理计算

由于碳纳米管（CNTs）载Pt催化剂中,CNTs与Pt纳米颗粒间的交互作用弱,导致两者间导电性较差,并且容易引起Pt脱落或团聚。本文采用第一性原理对Pt原子在CNTs封闭端部的吸附行为进行了研究,发现B掺杂可以使（5,5）型和（9,0）型CNTs与Pt间的平均吸附能分别提高12.7%和19.6%,N掺杂可以使（5,5）型和（9,0）型CNTs与Pt间的平均吸附能分别提高22.4%和18.4%,并且CNTs与Pt间的电荷转移量较管壁吸附也得到了明显提升,同时B或N掺杂使CNTs-Pt体系的稳定性最高可分别提升133.8%和237.3%,说明在CNTs端部掺杂B或N可提高CNTs载Pt催化剂的性能。     

Fabrication of PtNi bimetallic nanoparticles supported on multi-walled carbon nanotubes

Platinum/nickel bimetallic nanoparticles supported on multi-walled carbon nanotubes (xPtNi/CNTs) were synthesised. The fabrication process includes the chemical modification on the graphene surface of CNTs by acid treatment and the subsequent deposition of Pt or PtNi bimetallic nanoparticles with different compositions of Pt (x = 100, 90, 80 and 70 wt%). The deposition was carried out using ethylene glycol as a reducing agent in the polyol method or using poly(amidoamine) dendrimer as a platform and sodium borohydride as a reducing agent to load the metal nanoparticles on the CNT surface. The structures of the produced PtNi/CNT nanoparticles were investigated by ultraviolet absorption spectra, X-ray diffraction (XRD) and the composite ratio consisting of 70 wt% of metal content and 30 wt% of CNTs was confirmed by the thermogravimetric analysis. The morphology and the phase identification of the produced PtNi/CNT nanoparticles were investigated by high-resolution scanning electron microscope, transmission electron microscope and XRD measurements. It was observed that the deposited Pt and PtNi bimetallic nanoparticles on the surface of CNTs had average particle sizes of 2–16 nm, when they were prepared from the polyol method. On the other hand, the PtNi/CNT nanoparticles prepared by using a dendrimer as an intermediate had a smaller particle size and more uniform size distribution of the quantum dot size ranged from 2 to 4 nm.