Proton-Exchange Sulfonated Poly （ether ether ketone） （SPEEK）/SiOx-S Composite Membranes in Direct Methanol Fuel Cells

A sulfonated poly（ether ether ketone） （SPEEK） membrane with a fairly high degree of sulfonation （DS） can swell excessively and even dissolve at high temperature. To solve these problems, insolvable functionalized silica powder with sulfonic acid groups （SiOx-S） was added into the SPEEK matrix （DS = 55.1%） to prepare SPEEK/ SiOx-S composite membranes. The decrease in both the swelling degree and the methanol permeability of the membranes was a dose-dependent result of addition of the SiOx-S powder. Pure SPEEK membrane swelled 52.6% at 80℃, whereas the SPEEK/SiOx-S （15%, by mass） membrane swelled only 27.3% at the same temperature. From room temperature to 80℃, all SPEEK/SPEEK/SiOx-S composite membranes had methanol permeability of about one order of magnitude lower than that ofNafion115. Compared with pure SPEEK membranes, the addition of the SiOx-S powder not only leads to higher proton conductivity, but also increases the dimensional stability at higher temperatures, and greater proton conductivity can be achieved at higher temperature. The SPEEK/SiO4-S （20%, by mass） membrane could withstand temperature up to 145℃, at which in 100% relative humidity （RH） its proton conductivity exceeded slightly that of Nafion 1 15 membrane and reached 0.17 S·cm^-1, while pure SPEEK membrane dissolved at 90℃. The SPEEK/SiOx-S composite membranes are promising for use in direct methanol fuel cells because of their good dimensional stability, high proton conductivity, and low methanol permeability.

Waste Water Treatment in Direct Borohydride Fuel Cell with Bipolar Membrane

It was established that application of bipolar membrane in a direct borohydride fuel cell (DBFC) with H2O2 co-generation enabled to keep constant pH in catholyte within 2.5 - 3.2 limits, which allowed us to carry out treatment of water polluted by organic compounds in fuel cell catholyte. Treatment of water was carried out by electro-Fenton and photo-electro-Fenton methods. With the view of efficiency, photo-electro-Fenton method of treatment was the most efficient, which enabled to decrease COD of catholytes containing (in each case) phenol, valsaren, 400 g/L dymethoate (BI-58) and valsaciper from 500 ppm to 30, 11, 9 and 3 ppm, respectively after 180 min treatment. By increasing the catholyte temperature from 20℃?to 40℃?in the same period, phenol COD fell to 5 ppm.

On-line Measurement for Ohmic Resistance in Direct Methanol Fuel Cell by Current Interruption Method

Electrochemical impedance spectroscopy (EIS) is widely used in fuel cell impedance analysis. However, for ohmic resistance (R Ω), EIS has some disadvantages such as long test period and complex data analysis with equivalent circuits. Therefore, the current interruption method is explored to measure the value of RΩ in direct methanol fuel cells (DMFC) at different temperatures and current densities. It is found that RΩ decreases as temperature increase, and decreases initially and then increases as current density increases. These results are consistent with those measured by the EIS technique. In most cases, the ohmic resistances with current interruption (R iR ) are larger than those with EIS (R EIS ), but the difference is small, in the range from –0.848% to 5.337%. The errors of R iR at high current densities are less than those of R EIS . Our results show that the R iR data are reliable and easy to obtain in the measurement of ohmic resistance in DMFC.

Highly active and durable Pd-Cu catalysts for oxygen reduction in alkaline exchange membrane fuel cells

A Pd-Cu catalyst, with primary B2-type phase, supported by VulcanXC-7R carbon was synthesized via a solvothermal method. The catalysts were physically and electrochemically characterized by X-ray diffraction （XRD）, X-ray photoelectron spectroscopy （XPS）, trans- mission electron microscopy （TEM） and both cyclic and linear sweep voltammetry using a rotating disk electrode （RDE）. During the RDE testing, the half-wave potential of the Pd-Cu/Vulcan catalyst was 50 mV higher compared to that of commercial Pt/C catalyst for the oxygen reduction reaction （ORR） in alkaline media. The Pd-Cu/Vulcan exhibited a specific activity of 1.27 mA/cm2 and a mass activity of 0.59 A/mgpd at 0.9 V, which were 4 and 3 times greater than that of the commercial Pt/C catalyst, respectively. The Pd-Cu/Vulcan catalyst also showed higher in-situ alkaline exchange membrane fuel cell （AEMFC） performance, with operating power densities of 1100 MW/cm2 operating on H2/O2 and 700 MW/cm2 operating on H2/Air （CO2-free）, which were markedly higher than those of the commercial Pt/C. The Pd-Cu/ Vulcan catalyst also exhibited high stability during a short-term, in-situ AEMFC durability test, with only around 11% performance loss after 30 hours of operation, an improve- ment over most AEMFCs reported in the literature to date.

Proton-exchange Sulfonated Poly（ether ether ketone）/Sulfonated Phenolphthalein Poly（ether sulfone） Blend Membranes in DMFCs

A sulfonated poly（ether ether ketone） （SPEEK） membrane with fairly high degree of sulfonation （DS） swells excessively and even dissolves at high temperature. To solve these problems, sulfonated phenolphthalein poly（ether sulfone） （SPES-C, DS= 53.7%） is blended with the SPEEK matrix （DS= 55.1%, 61.7%） to prepare SPEEKJSPES-C blend membrane. The decrease in swelling degree and methanol permeability of the membrane is dose-dependent. Pure SPEEK （DS = 61.7%） membrane dissolves completely in water at 70℃, whereas the swelling degree of the SPEEK （DS = 61.7%）/SPES-C （40%, by mass） membrane is 29.7% at 80℃. From room temperature to 80℃, the methanol permeability of all SPEEK （DS = 55.1%）/SPES-C blend membranes is about one order of magnitude lower than that of Nafion 115. At higher temperature, the addition of SPES-C polymer increases the dimensional stability and greater proton conductivity can be achieved. The SPEEK （DS = 55.1%）/SPES-C （40%, by mass） membrane can withstand temperatures up to 150℃. The proton conductivity of SPEEK （DS = 55.1%）/SPES-C （30%, by mass） membrane approaches 0.16 S·cm^-1, matching that of Nafion 115 at 140℃ and 100% RH, while pure SPEEK （DS = 55.1%） membrane dissolves at 90℃. The SPEEK/SPES-C blend membranes are promising for use in direct methanol fuel cells because of their good dimensional stability, high proton conductivity, and low methanol permeability.

Preparation and evaluation of crosslinked sulfonated polyphosphazene with poly(aryloxy cyclotriphosphazene) for proton exchange membrane

Several crosslinked proton exchange membranes with high proton conductivities and low methanol permeability coefficients were prepared, based on the sulfonated poly[(4-fluorophenoxy)(phenoxy)] phosphazene(SPFPP) and newly synthesized water soluble sulfonated poly(cyclophosphazene)(SPCP) containing clustered flexible pendant sulfonic acids. The structure of SPCP was characterized by fourier transform infrared spectroscopy(FTIR) and ~1H NMR spectra. The membranes showed moderate proton conductivities and much lower methanol permeability coefficients when compared to Nafion 117. Transmission electron microscopy(TEM) results indicated the well-defined phase separation between the locally and densely sulfonated units and hydrophobic units, which induced efficient proton conduction. In comparison with SPFPP membrane, the proton conductivities, oxidative stabilities and mechanical properties of crosslinked membranes remarkably were improved. The selectivity values of all the crosslinked membranes were also much higher than that of Nafion 117(0.74×10~5S· s/cm~3). These results suggested that the c SPFPP/SPCP membranes were promising candidate materials for proton exchange membrane in direct methanol fuel cells.

Toward alkaline‑stable anion exchange membranes in fuel cells:cycloaliphatic quaternary ammonium‑based anion conductors

Anion exchange membrane(AEM)stability has been a long-standing challenge that limited the widespread development and adoption of AEM fuel cells(AEMFCs).The past five years have been a period of exceptional progress in the development of several alkaline-stable AEMs with remarkable both ex situ and in situ AEMFC stability.Certain cycloaliphatic quaternary ammonium(cQA)(mainly five-and six-membered)based AEMs appear to be among those having the most promising overall performance.In this review,we categorize cQAs as cage-like(such as quaternized 1,4-diazabicyclo[2.2.2]octane,(QDABCO)and quinuclidinium),non-cage-like(such as pyrrolidinium and piperidinium)and N-spirocyclic(such as 6-azonia-spiro[5.5]undecane(ASU)).The degradation mechanisms of categorized cQAs are first elucidated.Through an understanding of how the cations are attacked by strongly nucleophilic OH–,improved structural design of incorporating alkaline-stable cations into AEMs is facilitated.Before a detailed description and comparison of the alkaline stability of cQAs and their respective AEMs,current protocols for the assessment of alkaline stability are discussed in detail.Furthermore,the initial AEMFC performance and fuel cell performance stability based on cQA AEMs are also examined.The main focus and highlight of this review are recent advances(2015–2020)of cQA-based AEMs,which exhibit both excellent cation and membrane alka-line stability.We aim to shed light on the development of alkaline-stable cQA-type AEMs,which are trending in the AEM community,and to provide insights into possible solutions for designing long-lived AEM materials.

Functionalised Poly(Vinyl Alcohol)/Graphene Oxide as Polymer Composite Electrolyte Membranes

Crosslinked poly(vinyl alcohol)(PVA)based composite films were prepared as polyelectrolyte membranes for low temperature direct ethanol fuel cells(DEFC).The membranes were functionalised by means of the addition of graphene oxide(GO)and sulfonated graphene oxide(SGO)and crosslinked with sulfosuccinic acid(SSA).The chemical structure was corroborated and suitable thermal properties were found.Although the addition of GO and SGO slightly decreased the proton conductivity of the membranes,a significant reduction of the ethanol solution swelling and crossover was encountered,more relevant for those functionalised with SGO.In general,the composite membranes were stable under simulated service conditions.The addition of GO and SGO particles permitted to buffer the loss and almost retain similar proton conductivity than prior to immersion.These membranes are alternative polyelectrolytes,which overcome current concerns of actual commercial membranes such as the high cost or the crossover phenomenon.

Poly(vinyl alcohol)/Poly(diallyldimethylammonium chloride)anionexchange membrane modified with multiwalled carbon nanotubes for alkaline fuel cells

Hydroxyl anion conducting membrane composed of poly(vinyl alcohol)(PVA),poly(diallyldimethylammonium chloride)(PDDA),and hydroxylated multiwalled carbon nanotubes(MWCNTs-OH)have been synthesized via a facile blending-casting method assisted by a hot-chemical cross-linking process.Fourier-transform infrared spectroscopy(FTIR)and scanning electron microscopy(SEM)showed that PDDA and MWCNTs-OH were successfully introduced into the PVA matrix and MWCNTs-OH could effectively improve the network structure of the membrane.With the addition of MWCNTs-OH,many properties of the membranes such as thermal,chemical,mechanical stability and swelling property were improved significantly.Most prominent is the improvement of mechanical property,where the PVA/PDDA/MWCNTs-OH(1:0.5/3 wt.%)membrane showed high tensile strength of 40.3 MPa,tensile elongation of 12.3%and high Young's modulus of 782.8 MPa.Moreover,MWCNTs-OH bound the polymer chains in the membranes more compactly,resulting in decreased water uptake.By tuning the mass fraction of PVA,PDDA,and MWCNTs-OH in the membrane,the maximum OH-conductivity(0.030 S cm^(-1)at room temperature)was achieved for the composition of 0.5 wt.%MWCNTs-OH doped with the PVA:PDDA(1:0.5 by mass)blend.The membranes showed excellent oxidative stability when treated with both a solution of H_(2)O_(2)(30 wt.%)at room temperature and in a hot KOH solution(8 M)at 80℃.Based on the full aliphatic structure membrane(PVA/PDDA-OH/1 wt.%MWCNTs-OH),membrane electrode assemblies(MEAs)fabricated with Pt/C cathode catalyst can achieve power densities of 41.3 mW cm^(-2)and 66.4 mW cm^(-2)in a H_(2)/O_(2)system at room temperature and 40℃,respectively.Using CoPc as the Pt-free cathode catalyst,power densities of 9.1 mW cm^(-2)and 14.0 mW cm^(-2)at room temperature and 40℃ were obtained,respectively.

Semi-interpenetrating polymer networks toward sulfonated poly(ether ether ketone) membranes for high concentration direct methanol fuel cell

Low methanol permeability of proton exchange membranes (PEMs) is greatly important for direct methanol fuel cells (DMFCs). Here, sulfonated poly (ether ether ketone) (SPEEK) based semiinterpenetrating polymer networks (semi-IPNs) are successfully prepared by interpenetrating SPEEK into the in-situ synthesized crosslinking networks. The polymeric networks are formed by the covalent bonds between bromobenzyl groups of bro mo methylated poly (phenylene oxide) and amine groups of diamine linkers as well as the ionic bonds between amine species and sulfonated groups. Two linkers without and with sulfonated groups are applied to fabricate the semi-IPNs. The core properties of the membranes, like phase separation, water uptake, proton conductivity and methanol permeability, are systematically studied and compared. The DMFCs assembled by using the semi-IPN membranes display better performance than Nafion 117 in high concentration methanol solutions. The present work provides a facile way to prepare PEMs with enhanced DMFC performance.

Novel highly active carbon supported ternary PdNiBi nanoparticles as I anode catalyst for the alkaline direct ethanol fuel cell

The study focuses on the in flue nee of Ni and Bi on alkali me etha nol oxidati on reacti on (EOR) activities, stabilities and structure characteristics of carb on supported Pd-based nano catalysts (Pd/C, Pd6oNi4o/C, Pd6oBi4o/C, Pd6oNi2oBi2o/C) by cyclic voltammetry/chr ono amperometry using rotating disk electrode and various physico-chemical methods such as X-ray powder diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy coupled with energy dispersive X-ray spectroscopy and inductively coupled plasma optical emission spectrometry. Nickel generates more adsorbed OH on the Pd catalyst surface than Bi and promotes the oxidation of adsorbed ethanol species. This results in a low onset potential toward ethanol oxidation with high current density. The presenee of Bi facilitates high toleranee toward various reaction in termediates resulting from the incomplete etha nol oxidation, but might also initiate the agglomerati on of Pd nano particles. The no vel Pd60Ni20Bi20/C nanocatalyst displays exceptional byproduct toleranee, but only satisfying catalytic activity toward ethanol oxidation in an alkaline medium. Therefore, the EOR performanee of the novel carbon supported ternary PdxNiyBiz anode catalyst with various atomic variations (Pd70Ni25Bi5/C, Pd70Ni20Bi10/C, Pd80Ni10Bi10/C and Pd40Ni20Bi40/C) using the common instant reduction synthesis method was further optimized for the alkaline direct ethanol fuel cell. The carbon supported Pd:Ni:Bi nano catalyst with atomic ratio of 70:20:10 displays outsta nding catalytic activity for the alkaline EOR compared to the other PdxNiyBiy/C nanocatalysts as well as to the benchmarks Pd/C, Pd60Ni40/C and Pd60Bi40/C. The synergy and the optimal content in consideration of the oxide species of Pd, Ni and Bi are crucial for the EOR kinetic enhancement in alkaline medium.

Sulfonated poly(ether ether ketone)/zirconium tricarboxybutylphosphonate composite proton-exchange membranes for direct methanol fuel cells

Sulfonated poly(ether ether ketone)(SPEEK)is a very promising alternative membrane material for direct methanol fuel cells.However,with a fairly high degree of sulfonation(DS),SPEEK membranes can swell excessively and even dissolve at high temperature.This restricts mem-branes from working above a high tolerable temperature to get high proton conductivity.To deal with this contra-dictory situation,insolvable zirconium tricarboxybutyl-phosphonate(Zr(PBTC))powder was employed to make a composite with SPEEK polymer in an attempt to improve temperature tolerance of the membranes.SPEEK/Zr(PBTC)composite membranes were obtained by casting a homogeneous mixture of Zr(PBTC)and SPEEK in N,N-dimethylacetamide on a glass plate and then evaporating the solvent at 60℃.Many characteristics were investigated,including thermal stability,liquid uptake,methanol permeability and proton conductivity.Results showed significant improvement not only in tem-perature tolerance,but also in methanol resistance of the SPEEK/Zr(PBTC)composite membranes.The mem-branes containing 30 wt-%,40 wt-% of Zr(PBTC)had their methanol permeability around 10^(-7) cm^(2)·s^(-1) at room temperature to 80℃,which was one order of magnitude lower than that of Nafion H 115.High proton conductivity of the composite membranes,however,could also be achieved from higher temperature applied.At 100% rela-tive humidity,above 90℃ the conductivity of the compo-site membrane containing 40 wt-% of Zr(PBTC)exceeded that of the Nafion H 115 membrane and even reached a high value of 0.36 S·cm^(-1) at 160uC.Improved applicable tem-perature and high conductivity of the composite membrane indicatedits promisingapplication in DMFC operationsat high temperature.

Modified Nafion Polymer Electrolyte Membranes by 7-Ray Irradiation Used in Direct Methanol Fuel Cells

Modification of the commercial polymer electrolyte membrane （PEM） Nation 117 by γ-ray irradiation to produce an improved proton exchange membrane for direct methanol fuel cells （DMFCs） was described. The Nation 117 membrane was exposed under γ-ray irradiation circumstance with the irradiation doses from 103 to 105 Gy. Subsequently the properties of the membrane itself, in terms of swelling ratio, water uptake rate, proton conductivity and methanol permeability, together with the performance of its membrane electrode assembly （MEA） in DMFC were analyzed and contrasted with the untreated material. When the Nation 117 membrane was exposed under γ-ray irradiation circumstance, the degradation and crosslinking reactions occurred at the same time. Specific scopes of the γ-ray irradiation dose may cause the membrane crosslinking, thus reduce the membrane swelling ratio and decrease the methanol crossover. By reducing the membrane swelling ratio and methanol permeation, the single DMFC with the modified Nation 117 membrane produced reasonable power density performance as high as 32 W/m2 under 2 mol/L methanol solution at room temperature.

Tunable nitrogen crafted 2D-graphene nano-hybrid from industrial expansive and ecological approach as robust cathode microporous layer to improve performance of a direct methanol fuel cell

In this work, the excess water-stagnation issue in the high current region in direct methanol fuel cells(DMFCs) is resolved by using atomic precision modulated nitrogen-crafted graphene(NG) in the cathode microporous layer by utilizing simplistic,industrial-expansive and ecological strategy. Few-layer 2D-graphene(~2–5 nm thickness) is prepared by bath sonication approach from abundant feedstock-graphite and is treated with nitric acid to yield 1.8 wt.% uniformly dispersed nitrogen containing NG. Specifically, 1:4 weight ratio NG:carbon-black(CB) hybrid architecture, displays 0.252 V in 370 mA cm^(-2) with the peak power density of 93.4 mW cm^(-2), improving cell power density by 45.6% compared with standard one at 60℃ and 1 mol/L methanol/oxygen conditions at ultra-low catalyst loadings and displaying exceptional stability. Atomic insights into NG reveal that interplay between bonding configurations, altered hydrophobic/hydrophilic porosity of graphene(10.6% less wettability from contact angle and 13.1% high electrode porosity measurements) contribute to the better mass-transport-porogenic effect(16.3% high oxygen-permeability), mildly affecting the electron pathway(6.5% reduced in-plane electrical conductivity),overall significantly improving cell performance. Altogether, this work delivers multiple advantages, i.e., the usage of material from facile, sustainable and cost-effective routes, while improving DMFC performance with potential industrial promise.

Molecular dynamics simulation of alkaline electrolyte diffusion in anion exchange membrane

During the operation of alkaline direct liquid fuel cells,the alkaline electrolyte is usually needed in the anode electrode to accelerate the electrochemical reaction kinetics of the liquid fuel.However,the crossover of the alkaline solution in the anode through the anion exchange membrane to the cathode can increase the transfer resistance of the oxygen in the cathode.In order to reduce the crossover of the alkaline solution,the diffusion process of the alkaline solution in the anion exchange membrane needs to be fully understood.In this work,interface models of anion exchange membrane-alkaline electrolytes are established based on the cell structure of the quaternary ammonium polysulfone(QAPS)membrane to simulate the dynamic process of the alkaline solution in the membrane.The effect of the type and the concentration of the alkaline solution on the transportation of the metal ions and OH^-in the membrane are studied.The results show that the agglomeration of Na+is formed more easily than K^+in the interface model.Because of the strong interaction of Na^+on OH^-,OH^-ions appear to be concentrated,resulting in that the diffusion coefficients of the metal ion and OH^-in the in Na^+solution are lower than those in the K^+solution.In addition,with the raised concentration of electrolyte solution,the aggregation degrees of the metal ions and OH^-can be increased,which means an enlarged mass transfer resistance of the components.Furthermore,by adding a polytetrafluoroethylene(PTFE)layer on the QAPS membrane,the distribution of metal ions tends to be concentrated,and the number of hydrophilic channels in the QAPS membrane is reduced,which significantly increases the alkali resistance of the anion exchange membrane.

阴离子交换膜离子传导率与耐碱稳定性研究进展

碱性膜电解水制氢和燃料电池技术是氢能产业链上的重要产氢和用氢技术。作为碱性膜电解槽及燃料电池的核心部件,阴离子交换膜承担着传递氢氧根离子、阻隔气体渗透、分隔正负两极的重要作用,决定着电化学过程效率和性能.现有阴离子交换膜的氢氧根传导率偏低和耐碱稳定性不高的问题严重制约着产氢和氢能转化效率.本文综述了近年来面向碱性膜电解水制氢和燃料电池应用的阴离子交换膜的发展动态,特别是在强化离子传导率、提高耐碱稳定性方面的方法和进展,以及膜材料化学组成和结构对膜性能的影响.

碱性聚合物电解质膜的表面锥形阵列结构提升燃料电池性能

燃料电池作为一种清洁高效的能量转换装置,被认为是构建未来社会可再生能源结构的关键一环。不同于质子交换膜燃料电池(PEMFC),碱性聚合物电解质燃料电池(APEFC)的出现使非贵金属催化剂的使用成为可能,因而受到了日益广泛的关注和研究。APEFC的关键结构是膜电极,主要由聚合物电解质膜和阴阳极(含催化层、气体扩散层)组成,膜电极是电化学反应发生的场所,其优劣直接决定着电池性能的好坏。因此,基于现有的碱性聚合物电解质及催化剂体系,如何构筑更加优化的膜电极结构,使APEFC发挥出更高的电池性能是亟待开展的研究。本文首先通过模板法在碱性聚合物电解质膜的表面构建出有序的锥形阵列,再将具有阵列结构的一侧作为阴极来构筑膜电极,同时,作为对比,制备了由无阵列结构的聚合物电解质膜构筑而成的膜电极,最后对基于两种不同膜电极的APEFC的电化学性能进行了对比研究。实验结果表明,锥形阵列结构可以将APEFC的峰值功率密度由1.04 W·cm^(−2)显著提高到1.48 W·cm^(−2),这主要归因于在APEFC的阴极侧具有锥形阵列结构的聚合物电解质膜的亲水性的提升和催化剂电化学活性面积的增加。本工作为碱性聚合物电解质燃料电池的膜电极结构设计与优化提供了新思路。

高阻醇PVDF/超支化聚酰胺共混质子交换膜的制备及性能

为了制备应用于直接甲醇燃料电池的高阻醇质子交换膜,采用溶液浇铸法,将聚偏氟乙烯(PVDF)与自制的超支化聚酰胺(HBPA)按质量比1∶1,1∶2,1∶3和1∶4制备成共混膜用作质子交换膜,分别编号为PH1-1,PH1-2,PH1-3和PH1-4。在共混过程中,PVDF中的氟基基团(—F)与HBPA中的端羧基基团(—COOH)之间形成了分子间氢键,大量氢键的形成在共混膜中构建出网状交联结构。测试了共混膜的甲醇渗透性能、质子电导率、吸水率和溶胀率、拉伸性能及热稳定性等重要性能。结果表明,构建的网状交联结构有效阻止了甲醇的渗透,使4种共混膜表现出良好的阻醇性能,其中共混膜PH1-1的甲醇渗透率低至5.41×10^(-7)cm^(2)/s,比商用Nafion 117膜低一个数量级,其拉伸强度高达38.24 MPa,是商用Nafion 117的两倍多。PH1-4共混膜的质子电导率最大,80℃时达到2.96×10^(-2)S/cm。采用相对选择性作为衡量质子电导率和甲醇渗透性的综合指标,发现PH1-4在4种膜中表现最佳。由此可见,适当设计和构建网状交联结构能有效提高质子交换膜的阻醇性能,并可对其它性能进行调控。