High-performance imidazole-containing polymers for applications in high temperature polymer electrolyte membrane fuel cells

This work focuses on the development of high temperature polymer electrolyte membranes(HT-PEMs)as key materials for HT-PEM fuel cells(HT-PEMFCs).Recognizing the challenges associated with the phosphoric acid(PA) doped polybenzimidazole(PBI) membranes,including the use of carcinogenic monomers and complex synthesis procedures,this study aims to develop more cost-effective,readily synthesized,and high-performance alternatives.A series of superacid-catalyzed polyhydroxyalkylation reactions have been carefully designed between p-terphenyl and aldehydes bearing imidazole moieties,resulting in a new class of HT-PEMs.It is found that the chemical structure of aldehyde-substituted N-heterocycles significantly impacts the polymerization reaction.Specifically,the use of 1-methyl-2-imidazole-formaldehyde and 1 H-imidazole-4-formaldehyde monomers leads to the formation of high-viscosity,rigid,and ether-free polymers,denoted as PTIm-a and PTIm-b.Membranes fabricated from these polymers,due to their pendent imidazole groups,exhibit an exceptional capacity for PA absorption.Notably,PTIm-a,carrying methylimidazole moieties,demonstrates a superior chemical stability by maintaining morphology and structural stability during 350 h of Fenton testing.After being immersed in 75 wt% PA at 40℃,the PTIm-a membrane reaches a PA content of 152%,maintains a good tensile strength of 13.6 MPa,and exhibits a moderate conductivity of 50.2 mS cm^(-1) at 180℃.Under H_(2)/O_(2) operational conditions,a single cell based on the PTIm-a membrane attains a peak power density of 732 mW cm^(-2) at 180℃ without backpressure.Furthermore,the membrane demonstrates stable cycle stability over 173 h within 18 days at a current density of 200 mA cm^(-2),indicating its potential for practical application in HT-PEMFCs.This work highlights innovative strategies for the synthesis of advanced HT-PEMs,offering significant improvements in membrane properties and fuel cell performance,thus expanding the horizons of HT-PEMFC technology.

Sulfonated polybenzimidazole/amine functionalized titanium dioxide(s PBI/AFT) composite electrolyte membranes for high temperature proton exchange membrane fuel cells usage

The novel sulfonated polybenzimidazole(sPBI)/amine functionalized titanium dioxide(AFT) composite membrane is devised and studied for its capability of the application of high temperature proton exchange membrane fuel cells(HT-PEMFCs),unlike the prior low temperature AFT endeavors.The high temperature compatibility was actualized because of the filling of free volumes in the rigid aromatic matrix of the composite with AFT nanoparticles which inhibited segmental motions of the chains and improved its thermal stability.Besides,amine functionalization of TiO2 enhanced their dispersion character in the sPBI matrix and shortened the interparticle separation gap which finally improved the proton transfer after establishing interconnected pathways and breeding more phosphoric acid(PA) doping.In addition,the appeared assembled clusters of AFT flourished a superior mechanical stability.Thus,the optimized sPBI/AFT(10 wt%) showed 65.3 MPa tensile strength;0.084 S·cm^-1 proton conductivity(at 160℃;in anhydrous conditions),28.6% water uptake and PA doping level of 23 mol per sPBI repeat unit.The maximum power density peak for sPBI/AFT-10 met the figure of0.42 W·cm^-2 at 160℃(in dry conditions) under atmospheric pressure with 1.5 and 2.5 stoichiometric flow rates of H2/air.These results affirmed the probable fitting of sPBI/AFT composite for HT-PEMFC applications.

Water-induced electrode poisoning and the mitigation strategy for high temperature polymer electrolyte membrane fuel cells

Engineering failure of membrane electrode assembly caused by increasingly fuel poisoning in the high temperature polymer electrolyte membrane fuel cells fed with humidified reformate gases is firstly demonstrated herein this work. Based on the results of the in-situ environmental scanning electron microscope, electrochemical analyses, and limiting current method, a water-induced phosphoric acid invasion model is constructed in the porous electrode to elucidate the failure causations of the hindered hydrogen mass transport and the enhanced carbon monoxide poisoning. To optimize the phosphoric acid distribution under the inevitably humidified circumstance, a facile and effective strategy of constructing acid-proofed electrode is proposed and demonstrates outstanding stability with highly humidified reformate gases as anode fuel. This work discusses a potential defect that was rarely studied previously under practical working circumstance for high temperature polymer electrolyte membrane fuel cells, providing an alternative opinion of electrode design based on the fundamental aspects towards the engineering problems.

Performance Investigation of Membrane Electrode Assemblies for High Temperature Proton Exchange Membrane Fuel Cell

Different types of ABPBI (poly(2,5-benzimidazole)) membranes and polymer binders were evaluated to investigate the performance of MEAs for high temperature proton exchange membrane fuel cell (HT-PEMFC). The properties of the prepared MEAs were evaluated and analyzed by polarization curve, electrochemistry impedance spectroscopy (EIS), cyclic voltammetry (CV) and durability test. The results showed that MEA with modified ABPBI membrane (AM) has satisfactory performance and durability for fuel cell application. Compare to conventional PBI or Nafion binders, polytetrafluoroethylene (PTFE) and polyvinylidene difluoride (PVDF) are more attractive as binders in the catalyst layer (CL) of gas diffusion electrode (GDE) for HT-PEMFC.

Numerical Analysis of Temperature Distributions in Single Cell of Polymer Electrolyte Fuel Cell when Operated in Elevated Temperature Range

Abstract： The purpose of this study is to analyze the temperature distribution on the interface between the polymer electrolyte membrane and catalyst layer at the cathode in single cell of polymer electrolyte fuel cell when operated in elevated temperature range than usual. In this study, the interface between the polymer electrolyte membrane and catalyst layer at the cathode is named as reaction surface. This study has considered the 1D multi-plate heat transfer model estimating the temperature distribution on the reaction surface and verified with the 3D numerical simulation model solving many governing equations on the coupling phenomena of the polymer electrolyte fuel cell. The 3D numerical simulation model coverers a half size of actual cell including three straight parts and two turn-back corners, which can display the essential phenomena of single cell. The results from both models/simulations agreed well. The effects of initial operation temperature, flow rate, and relative humidity of supply gas on temperature distribution on the reaction surface have been investigated. Though the effect of flow rate of supply gas on temperature distribution on reaction surface has been small, low relative humidity of supply gas has caused higher temperature on the reaction surface compared to high relative humidity of the supply gas. The temperature rise of reaction surface from initial operation temperature has increased with the increasing in initial operation temperature of cell.

Impact of Separator Thickness on Temperature Distribution in Single Polymer Electrolyte Fuel Cell Based on 1D Heat Transfer

It is known from the New Energy and Industry Technology Development Organization (NEDO) roam map Japan, 2017 that the polymer electrolyte fuel cell (PEFC) power generation system is required to operate at 100°C for application of mobility usage from 2020 to 2025. This study aims to clarify the effect of separator thickness on the distribution of the temperature of reaction surface (Treact) at the initial temperature of cell (Tini) with flow rate, relative humidity (RH) of supply gases as well as RH of air surrounding cell of PEFC. The distribution of Treact is estimated by means of the heat transfer model considering the H2O vapor transfer proposed by the authors. The relationship between the standard deviation of Treact-Tini and total voltage obtained in the experiment is also investigated. We can know the effect of the flow rate of supply gas as well as RH of air surrounding cell of PEFC on the distribution of Treact-Tini is not significant. It is observed the wider distribution of Treact-Tini provides the reduction in power generation performance irrespective of separator thickness. In the case of separator thickness of 1.0 mm, the standard deviation of Treact-Tini has smaller distribution range and the total voltage shows a larger variation compared to the other cases.

The effect of grafted alkyl side chains on the properties of poly(terphenyl piperidinium) based high temperature proton exchange membranes

High temperature proton exchange membrane fuel cells(HT-PEMFCs)operating at elevated temperatures above 120℃ take advantage of feasible anode fuels and simplified water/heat management.A high temperature polymer electrolyte membrane(HT-PEM)is the core material for HT-PEMFCs.In this work,a series of phosphoric acid(PA)doped HT-PEMs based on poly(terphenyl piperidine)(PTP)tailored with alkyl groups are synthesized.Five different pendant alkyl groups(including methyl,propyl,pentyl,heptyl and decyl)are grafted onto the piperidine group through the Menshutkin reaction between PTP and alkyl halides.Compared with PTP and methyl grafted PTP(PTP-C1)membranes,the PTP-Cx membranes with long alkyl side chains exhibit improved PA doping contents and conductivities.The optimized pentylsubstituted PTP membrane(PTP-C5)possessed a reasonable PA doping content(202%after immersing in 85 wt%PA at 60℃),high proton conductivity(96 mS cm^(-1) at 180℃)and good tensile strength(4.6 MPa at room temperature).A H_(2)–air single cell equipped with PTP-C5/PA consequently achieved a high peak power density of 676 mW cm^(-2) at 210℃ without any humidification or backpressure.Thus,this work provides a simple method for preparing high-performance HT-PEMs.

Phosphorus induced activity-enhancement of Fe-N-C catalysts for high temperature polymer electrolyte membrane fuel cells

Fe-N-C materials with atomically dispersed Fe–N_(4) sites could tolerate the poisoning of phosphate,is regarded as the most promising alternative to costly Pt-based catalysts for the oxygen reduction in high temperature polymer electrolyte membrane fuel cells(HT-PEMFCs).However,they still face the critical issue of insufficient activity in phosphoric acid.Herein,we demonstrate a P-doping strategy to increase the activity of Fe-N-C catalyst via a feasible one-pot method.X-ray absorption spectroscopy and electron microscopy with atomic resolution indicated that the P atom is bonded with the N in Fe–N_(4) site through C atoms.The as prepared Fe-NCP catalyst shows a half-wave potential of 0.75 V(vs.reversible hydrogen electrode(RHE),0.1 M H_(3)PO_(4)),which is 60 and 40 mV higher than that of Fe-NC and commercial Pt/C catalysts,respectively.More importantly,the Fe-NCP catalyst could deliver a peak power density of 357 mW·cm^(−2)in a high temperature fuel cell(160℃),exceeding the non-noble-metal catalysts ever reported.The enhancement of activity is attributed to the increasing charge density and poisoning tolerance of Fe–N_(4) caused by neighboring P.This work not only promotes the practical application of Fe-N-C materials in HT-PEMFCs,but also provides a feasible P-doping method for regulating the structure of single atom site.

氢燃料电池用高速永磁同步电机性能的数值研究

在利用Maxwell方程组推导了高速永磁同步电机的二维电磁场控制方程的基础上,采用Bertotti铁耗分立模型计算电机铁耗,引入雷诺系数计算风摩损耗,用经典计算公式计算绕组铜耗和涡流损耗,以上损耗值转化为体积生热率施加到电机各发热部件作为温度场分析时的热源,并且考虑材料温变特性和定子非晶合金导热系数各向异性,使用流固耦合法建立了高速永磁电机温升预测模型。依据所建模型进行算例分析,应用Maxwell软件和Fluent软件研究了气隙槽宽、槽肩高和气隙长度对电机磁场、温度场的影响,研究表明气隙槽宽对电机磁场影响较小,适当增大气隙槽宽有利于电机散热。

S44535铁素体不锈钢高温氧化行为

为了探究稀土La对S44535铁素体不锈钢高温氧化行为的影响,采用加速氧化对添加0.26%La的S44535钢在800、900、1000℃下的静态空气中进行高温氧化研究。采用恒温氧化法对比S44535铁素体不锈钢在三种温度下的氧化动力学曲线,用扫描电镜(SEM)、能谱分析仪(EDS)和X射线衍射(XRD)对钢的氧化层进行表征分析,探究了稀土La对铁素体不锈钢高温抗氧化性能的影响。结果表明,氧化产物主要为Cr2O3和MnCr2O4,随着温度的升高,表面氧化膜增厚且更加致密,其外层富含Mn,内层富含Cr,说明稀土改变了氧化膜的生长方式,且呈现出较为优异的高温抗氧化性能。

高温质子交换膜燃料电池动态性能测试教学实验设计

该文结合科研热点,设计了具有创新性和研究性的“高温质子交换膜燃料电池动态性能测试实验”。实验研究了阳极流动和死端模式下高温质子交换膜燃料电池在阶跃电流条件下的动态响应。从实验理论基础、实验平台搭建、性能测试方法及内容、实验结果探讨分析等方面,展示了科学研究的全过程。该实验旨在培养和提升学生的实验素养、科研能力、创新能力和实践能力。

沉积温度对MOCVD法制备固体氧化物燃料电池GDC阻挡层性质的影响

致密的氧化钆掺杂的氧化铈(GDC)薄膜可以被应用于固体氧化物燃料电池(SOFC)的阴极LSCF与电解质YSZ的阻挡层,防止绝缘相SrZrO3的生成,从而提高电池的耐久性。本文以四(2,2,6,6-四甲基-3,5-庚二酮)铈(Ce(DPM)_(4))和三(2,2,6,6-四甲基-3,5-庚二酮)钆(Gd(DPM)_(3))为前驱体,采用智能化学气相沉积设备在723~923 K在YSZ陶瓷基板表面制备GDC薄膜,并研究了不同沉积温度对GDC薄膜的相组成、择优取向、宏观表面、微观结构和电化学性能的影响。在748~923 K时制备了具有(200)择优取向的淡黄色GDC薄膜,且GDC晶粒呈岛状生长模式。在873 K时得到了阻挡效果良好的(200)择优取向的淡黄色GDC薄膜。组装LSCF/GDC/YSZ/GDC/LSCF对称电池,在1073 K下测得电池阻抗为0.08Ω·cm^(2),活化能为1.52 eV,表明873 K为化学气相沉积法制备GDC薄膜的最佳沉积温度。

直接甲醇燃料电池离网供电应用研究

针对石油管道监测、司法监控等领域存在的离网供电不足问题,设计了离网供电系统,将自研的直接甲醇燃料电池DMFC(direct methanol fuel cell)与太阳能电池、蓄电池等进行集成,用于实现离网设备的不间断供电。自主研制的DMFC具有较高的甲醇燃料转化率;在低温-40℃、常温20℃、高温45℃的模拟环境试验中,DMFC起动正常且均能够稳定运行;高温、低温环境中电堆性能相比常温环境会有下降。在离网供电系统实际运行的3904 h内,DMFC经历了0~40℃的环境温度波动,电堆以160 mA·cm-2的电流密度运行了1491 h,其性能可保持为初始状态的94.7%。研究表明,DMFC具有较强的环境适应能力,有利于提高离网供电系统的可靠性。

运行参数对高温燃料电池物质分布与启动时间的影响研究

使用comsol软件,建立高温质子交换膜燃料电池电化学传热传质三维数值模型,通过改变电池的电压和入口温度,分析运行参数对电池内物质分布以及启动时间的影响。结果表明,随着进气温度的升高和电压的降低,电池反应物的消耗量及水的生成量在不断增加,启动时间也随之缩短。电压低于0.4V以下时,会导致阴极氧气不足产生“饥饿”现象。并且当进气温度高于150℃时,提高进气温度对启动时间的影响会大幅减少。即0.4V的启动电压及150℃的进气温度是一个比较合适的启动参数。

Research of special carbon nanobeads supported Pt catalyst for fuel cell through high temperature pyrolysis and deposition from novel phthalocyanine

The carbon nanobeads were prepared through high temperature pyrolysis and deposition from phthalocyanine. After surface's functionalization treatment of the carbon beads, the carbon nanobeads supported Pt catalyst was produced. The Pt/C catalyst was characterized by SEM, TEM, Raman spectrum, EDS and XRD methods. Combining the carbonaceous paper spreaded up with the catalyst with Nafion membrane, we made MEA electrode. The discharge curves indicated that this carbon nanobeads supported Pt is a good fuel cell catalyst with excellent performance, high activity and sign of a long-time life.

高温质子交换膜材料的研究进展

高温质子交换膜燃料电池(HT-PEMFC)凭借水管理系统简单、零碳排放和高效率的优势,有望发展成为下一代车用动力系统。然而,HT-PEMFC中的聚苯并咪唑(PBI)膜需借助磷酸传递质子(H^(+)),导致PBI溶胀,机械性能下降;游离的磷酸分子容易发生扩散,毒化催化剂,堵塞电极的多孔介质;且PBI聚合物极易被不完全反应产生的羟基自由基氧化,导致电池稳定性衰减。目前,国内外研究学者提出了不同的解决策略。然而,电池内是一个复杂的电化学体系,先进的膜材料及结构仍有待进一步深入研究。本综述简要介绍了HT-PEMFC中导致膜降解的机理,重点探讨了防止高温质子交换膜磷酸损失、氧化降解和机械降解的最新研究进展。最后,提出了石墨烯等二维材料将发挥巨大的优势,使高温质子交换膜材料的研究向增强型、超薄化方向发展。

Modeling of Packed Bed Methanol Steam Reformer Integrated with Tubular High Temperature Proton Exchange Membrane Fuel Cell

This work proposes a novel tubular structure of high-temperature proton exchange membrane fuel cell(PEMFC)integrated with a built-in packed-bed methanol steam reformer to provide hydrogen for power output.A two-dimensional axisymmetric non-isothermal model was developed in COMSOL Multiphysics 5.4 to simulate the performance of a tubular high temperature proton membrane fuel cell and a packed bed methanol reformer.The model considers the coupling multi-physical processes,including methanol reforming reaction,water gas shift reaction,methanol cracking reaction as well as the heat,mass and momentum transport processes.The sub-model of the tubular packed-bed methanol reformer is validated between 433 K and 493 K with the experimental data reported in the literature.The sub-model of the high temperature proton exchange fuel cell is validated between 393 K and 433 K with the published literature.Our results show that power output and temperature distribution of the integrated unit depend on methanol flow rates and working voltages.It was suggested that stable power generation performance of 0.14 W/cm_(2)and temperature drop in methanol steam reformer of≤10 K could be achieved by controlling the methanol space-time ratio of≥250 kg·s/mol with working voltage at 0.6 V,even in the absence of an external heat source.

电解制氢与高温燃料电池在电力行业的应用与发展

制氢和燃料电池技术是实现氢能和电能相互转换的关键技术,我国将氢能和燃料电池列为战略性能源技术,大型的能源电力企业也正在推动氢能和燃料电池技术的应用和发展。电解制氢能够将不稳定的可再生能源转化为氢能,实现大规模、季节性储能,在一定的范围内具有经济效益,是解决我国当前可再生能源消纳的途径之一。碱性电解水制氢是目前最成熟的电解制氢技术,发展的主要方向是降低制氢能耗、提高单台出力以及负荷深度调节。高温燃料电池具有小型高效、近零排放的突出优点,在冷热电三联供分布式发电和固定式发电领域具有广阔的应用前景,国外已初步实现高温燃料电池的商业化应用,国内的高温燃料电池市场需求也已显现,我国已掌握高温燃料电池发电的核心技术,具备应用示范推广的技术基础。

高温燃料电池发电技术分析

熔融碳酸盐燃料电池(MCFC)和固体氧化物燃料电池(SOFC)均可被固定电站应用。对SOFC以及MCFC的发展状况进行了论述,分析了SOFC的发展方向和存在的问题,以及MCFC的材料工艺、发展现状和存在的问题,并从制造成本、电池堆容量、材料体系、商业化示范等方面对2种高温燃料电池进行了比较分析。分析得出,适合我国绿色煤电计划的高温燃料电池发展技术路线是优先发展MCFC技术,利用国内外积累的MCFC研究成果,尽快实现MCFC的大型化与产业化。

高温燃料电池与燃气轮机相结合的混合发电系统

高温燃料电池与燃气轮机相结合的混合发电系统具有高效、环保和可靠的特性,这种新颖的混合发电系统在未来分布式发电领域具有广阔的应用前景。有不少专家和学者对其系统构成及匹配、系统性能等问题做了大量研究。目前已有高温燃料电池与燃气轮机混合发电系统成功运行,但仍有很多问题需要进行进一步的研究和探索,以使该混合发电系统早日实现商业化运行。本文综述了高温燃料电池与燃气轮机混合发电系统的研究现状,展望了该混合发电系统在未来的研究及发展前景。