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。     

Pt nanoparticle-reduced graphene oxide nanohybrid for proton exchange membrane fuel cells

A platinum nanoparticle-reduced graphene oxide (Pt-RGO) nanohybrid for proton exchange membrane fuel cell (PEMFC) application was successfully prepared. The Pt nanoparticles (Pt NPs) were deposited onto chemically converted graphene nanosheets via ethylene glycol (EG) reduction. According to the powder X-ray diffraction (XRD) pattern and transmission electron microscopy (TEM) analysis, the face-centered cubic Pt NPs (3-5 nm in diameter) were homogeneously dispersed on the RGO nanosheets. The electrochemically active surface area and PEMFC power density of the Pt-RGO nanohybrid were determined to be 33.26 m2/g and 480 mW/cm2 (maximum values), respectively, at 75 degrees C and at a relative humidity (RH) of 100% in a single-cell test experiment.     

质子交换膜燃料电池关键材料的研究进展EI北大核心CSCD

燃料电池是一种非常有前景的新能源体系。燃料电池不使用热力发动机,利用电极和电解质界面发生的化学反应直接将燃料的化学能转换成电能,反应不受卡诺循环限制,因此,具有高的能量转换效率。在燃料电池中,质子交换膜燃料电池(PEMFC)在便携式设备、交通运输以及固定装置领域具有重要的应用前景。然而,目前的PEMFC还存在一些问题,主要包括高成本、功率不足、稳定性差等问题,限制了其大规模商业化应用。这些问题的根本原因在于PEMFC中阴极催化剂、气体扩散层、质子交换膜和双极板等关键材料的成本和性能还不能满足PEMFC商业化的要求。要实现PEMFC的大规模应用,需要开发先进的阴极催化剂、气体扩散层、质子交换膜和双极板等关键材料。针对PEMFC对低成本、高性能先进材料的需求,本文综述了阴极催化剂、气体扩散层、质子交换膜和双极板等关键材料的研究进展以及应用面临的问题,并指出了未来的发展方向:加强铂合金催化剂以及金属-氮-碳(M-N-C)化合物催化剂的规模化制备工艺的探索;制备兼具高质子传导率和优异力学性能的质子交换膜;详细研究改性气体扩散层在不同的工况条件下对PEMFC性能的影响;开发具有优良耐蚀性和导电性的涂层或新型金属材料用于双极板。     

Progress in modified carbon support materials for Pt and Pt-alloy cathode catalysts in polymer electrolyte membrane fuel cells

H₂-fed polymer electrolyte membrane fuel cells (PEMFCs) are the most advanced fuel cell technology to date and continue to be of great interest as prospective energy sources in numerous applications, including for low/zero-emission electric vehicles, distributed power generators in homes, and small portable electronic devices. However, the commercialization of PEMFC technology has been greatly hindered by certain challenges, mainly the sluggish kinetics of the oxygen reduction reaction at the cathode and the high cost of Pt-based cathode catalysts, the latter presently accounting for over 55% of the total PEMFC cost. To overcome the limited stability of state-of-the-art Pt/C, Pt and Pt-alloy catalysts supported on modified carbon materials have garnered significant interest in recent years. It is therefore timely to compile a review that focuses on Pt and Pt-alloy catalysts supported on modified carbon materials, examining their current R&D status, applications, challenges, and future prospects. This review provides a systematic and comprehensive survey of current Pt and Pt-alloy PEMFC cathode catalysts in terms of materials selection and design, synthesis methods, and structural features, emphasizing how these various aspects relate to the catalysts’ physicochemical characterization and performance, and with the aim of shedding light on the future direction of PEMFC research.     

Nafion/silane nanocomposite membranes for high temperature polymer electrolyte membrane fuel cell

The polymer electrolyte membrane fuel cell (PEMFC) has been studied actively for both potable and stationary applications because it can offer high power density and be used only hydrogen and oxygen as environment-friendly fuels. Nafion which is widely used has mechanical and chemical stabilities as well as high conductivity. However, there is a drawback that it can be useless at high temperatures (> or = 90 degrees C) because proton conducting mechanism cannot work above 100 degrees C due to dehydration of membrane. Therefore, PEMFC should be operated for long-term at high temperatures continuously. In this study, we developed nanocomposite membrane using stable properties of Nafion and phosphonic acid groups which made proton conducting mechanism without water. 3-Aminopropyl triethoxysilane (APTES) was used to replace sulfonic acid groups of Nafion and then its aminopropyl group was chemically modified to phosphonic acid groups. The nanocomposite membrane showed very high conductivity (approximately 0.02 S/cm at 110 degrees C, <30% RH).     

Study of ceria-carbonate nanocomposite electrolytes for low-temperature solid oxide fuel cells

Composite and nanocomposite samarium doped ceria-carbonates powders were prepared by solid-state reaction, citric acid-nitrate combustion and modified nanocomposite approaches and used as electrolytes for low temperature solid oxide fuel cells. X-ray Diffraction, Scanning Electron Microscope, low-temperature Nitrogen Adsorption/desorption Experiments, Electrochemical Impedance Spectroscopy and fuel cell performance test were employed in characterization of these materials. All powders are nano-size particles with slight aggregation and carbonates are amorphous in composites. Nanocomposite electrolyte exhibits much lower impedance resistance and higher ionic conductivity than those of the other electrolytes at lower temperature. Fuel cell using the electrolyte prepared by modified nanocomposite approach exhibits the best performance in the whole operation temperature range and achieves a maximum power density of 839 mW cm(-2) at 600 degrees C with H2 as fuel. The excellent physical and electrochemical performances of nanocomposite electrolyte make it a promising candidate for low-temperature solid oxide fuel cells.     

A redox-stable efficient anode for solid-oxide fuel cells

Solid-oxide fuel cells (SOFCs) promise high efficiencies in a range of fuels. Unlike lower temperature variants, carbon monoxide is a fuel rather than a poison, and so hydrocarbon fuels can be used directly, through internal reforming or even direct oxidation. This provides a key entry strategy for fuel-cell technology into the current energy economy. Present development is mainly based on the yttria-stabilized zirconia (YSZ) electrolyte. The most commonly used anode materials are Ni/YSZ cermets, which display excellent catalytic properties for fuel oxidation and good current collection, but do exhibit disadvantages, such as low tolerance to sulphur and carbon deposition when using hydrocarbon fuels, and poor redox cycling causing volume instability. Here, we report a nickel-free SOFC anode, La0.75Sr0.25Cr0.5Mn0.5O3, with comparable electrochemical performance to Ni/YSZ cermets. The electrode polarization resistance approaches 0.2 Omega cm2 at 900 degrees C in 97% H2/3% H2O. Very good performance is achieved for methane oxidation without using excess steam. The anode is stable in both fuel and air conditions, and shows stable electrode performance in methane. Thus both redox stability and operation in low steam hydrocarbons have been demonstrated, overcoming two of the major limitations of the current generation of nickel zirconia cermet SOFC anodes.     

Synthesis and electrocatalytic oxygen reduction properties of truncated octahedral Pt3Ni nanoparticles

Pt₃Ni nanoparticles have been obtained by shape-controlled synthesis and employed as oxygen reduction electrocatalysts for proton exchange membrane fuel cells (PEMFC). The effects of varying the synthesis parameters such as the types of the capping agent and the reducing agent, and the reaction time have been systematically studied. The as-prepared Pt₃Ni nanoparticles were subjected to a butylamine-based surface treatment in order to prepare carbon-supported electrocatalysts. The Pt₃Ni electrocatalysts show an areaspecific activity of 0.76 mA/cm²(Pt) at 0.9 V in an alkaline electrolyte, which is 4.5 times that of a commercial Pt/C catalyst (0.17 mA/cm² (Pt)). The mass activity reached 0.30 A/mg(Pt) at 0.9 V, which is about twice that of the commercial Pt/C catalyst. Our results also show that the area-specific activities of these carbon-supported Pt₃Ni electrocatalysts depend strongly on the (111) surface fraction, which is consistent with the results of a study based on Pt₃Ni extended single-crystal surfaces.     

Permeation of solvents through disk type rice husk silica membrane modified with alkyl silylation reagents

Rice husk silica (RHS) which was obtained with thermal treatment of rice husk has the size of approximately 10 micrometer with 4-5 nm pore. RHS can be mold to a disk type membrane. The membrane may have submicron pore originated from the space among the particles, and the nano pores of the rice husk silica (RHS pore). Even it is difficult to adjust the size of the pores, we can suggest that the membrane shows different permeability for the organic/inorganic solvents if the affinity between the surface of the pores and the permeating molecule is changed. In this study, we investigated the permeation of the typical solvents such as water, ethanol and toluene to the RHS membranes sintered at 1100 degrees C, 1150 degrees C and 1200 degrees C and modified with triethoxymethyl silane (CH3)Si(C2H5O)3, diethoxydiemethyl silane (CH3)2Si(C2H5O)2 and ethoxytriemethyl silane (CH3)3Si (C2H5O). The result showed that permeability of original membranes for water (e.g., 1100 degrees C, 2.87 x 10(-3) mol/m2 s Pa) was larger than ethanol (1100 degrees C, 5.51 x 10(-4) mol/m2 s Pa) and toluene (1100 degrees C, 3.09 x 10(-4) mol/m2 s Pa) at the sintering temperatures. For the silane modified membranes, the permeability for water decreased drastically while those for ethanol and toluene increased.     

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.     

PEDOT-PSSA as an alternative support for Pt electrodes in PEFCs

Poly (3,4-ethylenedioxythiophene) (PEDOT) and poly (styrene sulphonic acid) (PSSA) supported platinum (Pt) electrodes for application in polymer electrolyte fuel cells (PEFCs) are reported. PEDOT-PSSA support helps Pt particles to be uniformly distributed on to the electrodes, and facilitates mixed electronic and ionic (H⁺-ion) conduction within the catalyst, ameliorating Pt utilization. The inherent proton conductivity of PEDOT-PSSA composite also helps reducing Nafion content in PEFC electrodes. During prolonged operation of PEFCs, Pt electrodes supported onto PEDOT-PSSA composite exhibit lower corrosion in relation to Pt electrodes supported onto commercially available Vulcan XC-72R carbon. Physical properties of PEDOT- PSSA composite have been characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy and transmission electron microscopy. PEFCs with PEDOT-PSSA-supported Pt catalyst electrodes offer a peak power-density of 810 mW cm⁻² at a load current-density of 1800 mA cm⁻² with Nafion content as low as 5 wt.% in the catalyst layer. Accordingly, the present study provides a novel alternative support for platinized PEFC electrodes.     

碳基纳米结构作为燃料电池催化剂载体的研究进展

质子交换膜燃料电池的主要商用催化剂是碳负载铂纳米粒子体系,其中碳的形式主要是碳黑。然而Pt属于贵金属,价格高、储量低,严重阻碍了PEMFCs的商业化进程。新型碳基纳米材料的不断涌现以及对其性能研究的不断深入,为解决上述问题带来了可能。越来越多的研究显示,基于新型碳基纳米材料的担载体系,不但能够提高Pt的利用率,降低所需的Pt担载量,还能提升催化剂的稳定性和催化活性等,从而高效地提升担载型催化剂的性价比。概述了近年来碳基纳米材料作质子交换膜燃料电池催化剂载体的研究进展,并讨论了未来的发展方向以促进质子交换膜燃料电池的大规模商用。     

锂离子电池PEO-LATP/LAGP陶瓷复合电解质膜的制备与性能表征

设计并制备了PEO-LATP/LAGP陶瓷复合电解质. 使用NASICON结构的Li_1.4Al_0.4Ti_1.6(PO₄)₃ (LATP)或 Li_1.5Al_0.5Ge_1.5(PO₄)₃ (LAGP)作为陶瓷基体, 以PEO为粘结剂, 得到了均匀、厚度仅为20 μm的复合电解质膜. 通过电化学性能表征发现当w(LATP/LAGP):w(PEO)=7:3时, 复合电解质膜具有最高的室温电导率, 达到0.186 mS/cm (PEO-LATP)与0.111 mS/cm (PEO-LAGP). 通过充放电循环实验表明, Li/复合电解质/LiCo1/3Ni1/3Mn1/3O2电池的首次放电容量达170 mAh/g. 使用PEO-LATP复合电解质的电池在循环时有较大的容量衰减, 而使用PEO-LAGP复合电解质则循环性能有明显的改善, 在10次循环后仍保持在150 mAh/g.     

络合剂对电沉积Fe/Pt循环伏安行为的影响

通过循环伏安法研究了C6H5O73-、C4H4O62-、C6H11O7-、C4H5O5-4种络合剂对硫酸亚铁、氯铂酸铵溶液循环伏安行为以及Fe/Pt电解液循环伏安行为的影响.结果表明,选取C6H14O7N2或C4H4O6Na2作为络合剂电沉积单质铁,能有效减小电解液的扩散控制,从而使电极反应以稳定的速度发生,最终获得较好的电沉积效果(若选用酒石酸钠为络合剂,则应适当增大硫酸亚铁的浓度,以提高电沉积时的极化电流大小);选用C4H4O6Na2为络合剂电沉积Fe/Pt多层膜时,亦能有效的减小溶液的扩散控制.     

Proton-conducting glass electrolyte

A new porous glass electrolyte consisting of heteropolyacids, i.e., phosphotungstic acid (PWA) and phosphomolybdic acid, was investigated and was found to yield a remarkably high proton conductivity of 1.014 S cm(-1) at 30 degrees C and 85% relative humidity. This is the first time such a high proton conductivity value has been reported for a heteropolyacid glass membrane. The glass was applied as the electrolyte for an H(2)/O(2) fuel cell, and a maximum power density of 41.5 mW/cm(2) at 32 degrees C was attained using this new PWA-containing electrode.     

Ethylene glycol oxidation on Pt and Pt-Ru nanoparticle decorated polythiophene/multiwalled carbon nanotube composites for fuel cell applications

A novel supporting material containing polythiophene (PTh) and multiwalled carbon nanotubes (MWCNTs) (PTh-CNTs) is prepared by in?situ polymerization of thiophene on carbon nanotubes using FeCl(3) as oxidizing agent under sonication. The prepared polythiophene/CNT composites are further decorated with Pt and Pt-Ru nanoparticles by chemical reduction of the corresponding metal salts using HCHO as reducing agent at pH = 11 (Pt/PTh-CNT and Pt-Ru/PTh-CNT). The fabricated composite films decorated with nanoparticles were investigated towards the electrochemical oxidation of ethylene glycol (EG). The presence of carbon nanotubes in conjugation with a conducting polymer produces a good catalytic effect, which might be due to the higher electrochemically accessible surface areas, electronic conductivity and easier charge-transfer at polymer/electrolyte interfaces, which allows higher dispersion of Pt and Pt-Ru nanoparticles. Such nanoparticle modified PTh-CNT electrodes exhibit better catalytic behavior towards ethylene glycol oxidation. Results show that Pt/PTh-CNT and Pt-Ru/PTh-CNT modified electrodes show enhanced electrocatalytic activity and stability towards the electro-oxidation of ethylene glycol than the Pt/PTh electrodes, which shows that the composite film is more promising for applications in fuel cells.     

Structural characterization and catalytic activity of Pt dendrimer encapsulated nanoparticles supported over Al2O3 for SCR of NOx

Pt/Al2O3 and Pt-Mg/Al2O3 nano composites were successfully prepared by dendrimer templated synthesis route. The obtained dendritic nanoparticles were dispersed in alumina support and they were evaluated for SCR of NOx using methane as reductant. Thermal analysis results of uncalcined samples revealed that the oxygen can accelerate the rate of dendrimer shell decomposition. X-ray diffractograms of 500 degrees C calcined samples disclosed the amorphous nature of materials, whereas 1000 degrees C air calcined samples showed enhanced crystallinity as well as diffraction pattern corresponding to Pt and PtO. HRTEM images of Pt40-G4OH dendritic nanoparticles showed uniform particulate distribution with average particle size of 2.4 nm. The STEM results of 0.5 Pt/Al2O3 sample calcined at 500 degrees C exhibited a wide range of particles between 2 and 20 nm. This indicates the huge segregation of platinum metal particles during impregnation and subsequent calcination. Among the synthesized materials 0.5 wt% Pt/Al2O3 sample showed excellent conversion and selectivity for SCR of NOx.     

Preparation of carbon supported binary Pt–M alloy catalysts (M = first row transition metals) by low/medium temperature methods

Carbon supported Pt alloyed with first row transition elements (Pt–M/C) is being used as improved cathode catalyst for low temperature fuel cells. These catalysts have been usually prepared by deposition of the non-precious metal onto pre-formed carbon supported platinum, followed by alloying at temperatures of the order or above 700 °C. As the thermal treatment at high temperature gives rise to an undesired metal particle growth, synthetic methods based on the simultaneous deposition of Pt and M on the carbon substrate, followed by thermal treatment at lower temperature have been developed. In this paper the formation of Pt–M/C by low/intermediate temperature methods is reviewed.Moreover, to investigate the effect of the conditions used in the synthesis on the Pt:M atomic ratio, the degree of alloying and the particle size, carbon supported Pt–Co electrocatalysts with nominal Pt:Co atomic ratio 75:25 were prepared by a low temperature chemical reduction of the precursors with sodium borohydride at two different temperatures and NaBH₄ concentrations. The physical characterization of these electrocatalysts was performed by energy dispersive X-ray analysis and X-ray diffraction.     

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．     

Hydroisomerization and hydrocracking of n-hexane on Pt/SAPO-5 and Pt/SAPO-11 catalysts

The activity, stability, and selectivity of a series of bifunctional Pt/SAPO-5 and Pt/SAPO-11 catalysts containing 0.5 wt% platinum, were compared for n-hexane transformation at 300–425°C and atmospheric, 3- and 5-bar hydrogen pressures. Hydrogen pressure had a strong influence on the activity, isohexane selectivity, and time-on-stream deactivation. Isomerization to isohexanes was the major reaction in both cases. However, Pt/SAPO-5 shows high activity and higher isohexane selectivity than Pt/SAPO-11 catalyst. The selectivity patterns found in this class of molecular sieve catalysts are well interpreted in terms of a series of reaction pathways incorporating both confinement effects and shape selectivity factors as being important in determining the observed product distribution.