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1.
Proton exchange membrane fuel cell (PEMFC) technology based on perfluorosulfonic acid (PFSA) polymer membranes is briefly reviewed. The newest development in alternative polymer electrolytes for operation above 100 °C is summarized and discussed. As one of the successful approaches to high operational temperatures, the development and evaluation of acid doped polybenzimidazole (PBI) membranes are reviewed, covering polymer synthesis, membrane casting, acid doping, physicochemical characterization and fuel cell testing. A high temperature PEMFC system, operational at up to 200 °C based on phosphoric acid‐doped PBI membranes, is demonstrated. It requires little or no gas humidification and has a CO tolerance of up to several percent. The direct use of reformed hydrogen from a simple methanol reformer, without the need for any further CO removal, has been demonstrated. A lifetime of continuous operation, for over 5000 h at 150 °C, and shutdown‐restart thermal cycle testing for 47 cycles has been achieved. Other issues such as cooling, heat recovery, possible integration with fuel processing units, associated problems and further development are discussed. 相似文献
2.
A quaternary ammonium polybenzimidazole (QPBI) membrane was synthesized for applications in intermediate temperature (100–200 °C) hydrogen fuel cells. The QPBI membrane was imbibed with phosphoric acid to provide suitable proton conductivity. The proton conductivity of the membrane was 0.051 S cm–1 at 150 °C with the PA acid loading level of 3.5 PRU (amount of H3PO4 per repeat unit of polymer QPBI). The QPBI membrane was characterized in terms of composition, structure and morphology by NMR, FTIR, SEM, and EDX. The fuel cell performance with the membrane gave peak power densities of 440 and 240 mW cm–2 using oxygen and air, respectively, at 175 °C. 相似文献
3.
A series of polybenzimidazoles (PBIs) incorporating main chain sulphonic acid groups were synthesised as random copolymers with p‐PBI in varying ratios using polyphosphoric acid (PPA) as both the polymerisation solvent and polycondensation reagent. The PPA process was used to produce high molecular weight phosphoric acid (PA) doped PBI gel membranes in a one‐step procedure. These membranes exhibit excellent mechanical properties (0.528–2.51 MPa tensile stress and 130–300% tensile strain) even at high acid doping levels [20–40 mol PA/PRU (polymer repeat unit)] and high conductivities (0.148–0.291 S cm–1) at elevated temperatures (>100 °C) with no external humidification, depending on copolymer composition. Fuel cell testing was conducted with hydrogen fuel and air or oxygen oxidants for all membrane compositions at temperatures greater than 100 °C without external feed gas humidification. Initial studies showed a maximum fuel performance of 0.675 V for the 25 mol% s‐PBI/75 mol% p‐PBI random copolymer at 180 °C and 0.2 A cm–2 with hydrogen and air, and 0.747 V for the same copolymer at 180 °C and 0.2 A cm–2 with hydrogen and oxygen. 相似文献
4.
High temperature polymer electrolyte membrane (HT‐PEM) fuel cell is often integrated with a light fossil fuel reformer to improve the fuel flexibility. Although the operation of HT‐PEM fuel cell does not rely on the humidification of the inlet gas, water vapor is found in the reformate gas which is fed to the HT‐PEM fuel cell. In this work, the influence of water content in the H2 to the cell performance of a HT‐PEM fuel cell is studied under different operating temperatures. Under lower operating temperature of 140 °C, the HT‐PEM fuel cell shows the best performance with low water content in the H2. With increasing water content, the cell performance decreases. Under the operating temperature of 160 °C, the best cell performance is achieved with an intermediate water content in the H2. While under high operating temperature of 180 °C, the cell performance shows an increasing trend with the increase in the water content. By measuring the impedance spectra of the HT‐PEM fuel cell, the reasons for the different influence of anode humidification in cell performance at different operating temperatures were investigated. 相似文献
5.
Three series of polybenzimidazole (PBI) random copolymers (2,5‐pyridine‐r‐meta‐PBI, 2,5‐pyridine‐r‐para‐PBI, and 2,5‐pyridine‐r‐2OH‐PBI) were synthesized and cast into phosphoric acid (PA) doped membranes using the PolyPhosphoric Acid (PPA) Process. Copolymer composition was adjusted using co‐monomers that impart high and low solubility characteristics to simultaneously control overall copolymer solubility and gel membrane stability. Measured under a static compressive force at 180 °C, copolymer membranes generally exhibited decreased creep compliance with increasing polymer content. Within each series of copolymer membranes, increasing polymer contents proportionally reduced the phosphoric acid/polymer repeat unit (PA/PRU) ratios and their respective proton conductivities. Some copolymer membranes exhibited comparable fuel cell performances (up to 0.66 V at 0.2 A cm−2 following break‐in) to para‐PBI (0.68 V at 0.2 A cm−2) and equal to 3,5‐pyridine‐based high solids membranes. Furthermore, 2,5‐pyridine copolymer membranes maintained a consistent fuel cell voltage of >0.6 V at 0.2 A cm−2 for over 8600 h under steady‐state operation conditions. Phosphoric acid loss was monitored during long‐term studies and demonstrated acid losses as low as 5.55 ng cm−2 h−1. The high‐temperature creep resistance and long‐term operational stabilities of the 2,5‐pyridine copolymer membranes suggest that they are excellent candidates for use in extended lifetime electrochemical applications. 相似文献
6.
In this work, seven commercially available high temperature (HT) membrane electrode assemblies (MEAs), using a phosphoric acid doped polybenzimidazole (PBI) membrane, were tested at six constant current densities during mostly around 540 h: 1, 0.6, 0.4, 0.2, 0.1, and 0 A cm−2. The MEA aged at 0.6 A cm−2 appears to be the less degraded one and the MEAs working at 0 and 1 A cm−2 seem to be the most degrading ones. Degradations are supposed to be mainly due to the carbon corrosion of electrodes and the loss of electrolyte with the MEA aged at 1 A cm−2. The characterization periods have a significant impact on cell ageing. The corrosion of carbon support is considered here to be the major degradation for the tests carried out between 0 and 0.6 A cm−2. A degradation rate was calculated using the voltage from the polarization curves and it appears to be more relevant compare to the degradation rate calculated using the voltage during endurance period. The modeling approach shows promising results and it seems that the electrochemical surface area, measured by cyclic voltammetry, can be included into the modeling in order to obtain higher parameter consistency. 相似文献
7.
High temperature proton exchange membrane fuel cells (HT‐PEMFCs) with phosphoric acid doped polybenzimidazole (PBI) membranes have gained tremendous attentions due to its attractive advantages over conventional PEMFCs such as faster electrochemical kinetics, simpler water management, higher carbon monoxide (CO) tolerance and easier cell cooling and waste heat recovery. In this study, a three‐dimensional non‐isothermal model is developed for HT‐PEMFCs with phosphoric acid doped PBI membranes. A good agreement is obtained by comparing the numerical results with the published experimental data. Numerical simulations have been carried out to investigate the effects of operating temperature, phosphoric acid doping level of the PBI membrane, inlet relative humidity (RH), stoichiometry ratios of the feed gases, operating pressure and air/oxygen on the cell performance. Numerical results indicate that increasing both the operating temperature and phosphoric acid doping level are favourable for improving the cell performance. Humidifying the feed gases at room temperature has negligible improvement on the cell performance, and further humidification is needed for a meaningful performance enhancement. Pressurising the cell and using oxygen instead of air all have significant improvements on the cell performance, and increasing the stoichiometry ratios only helps prevent the concentration loss at high current densities. 相似文献
8.
Sulfuric acid loaded polybenzimidazole (PBI) membranes were prepared with loading levels up to 10.58 (acid molecule per repeat unit of PBI) and characterized with Fourier transform infrared spectroscopy. Ionic conductivity of the PBI–H2SO4 membrane was found greater than that of the PBI–H3PO4 membrane. Through plane conductivity of a PBI–H2SO4 membrane with loading level 9.65 was >0.2 S cm–1 at 150 °C. However, the conductivity of PBI–H2SO4 membrane increased greatly with increasing relative humidity. Membrane electrode assemblies using PBI–H2SO4 membrane exhibited better power density performances with pre‐humidified H2 and air than that with none‐humidified gases. Polymer electrolyte membrane fuel cells with PBI–H2SO4 membrane in a single cell fixture demonstrated a peak power density >0.35 W cm–2 with H2 and air. 相似文献
9.
Fine particles of a solid proton conductor Sb0.2Sn0.8P2O7 were incorporated in PBI‐H3PO4 membranes with 20 wt.%. In SEM figures, the Sb0.2Sn0.8P2O7 particles exhibited even and uniform distribution in the PBI‐Sb0.2Sn0.8P2O7 membrane. Influences of the immersing time and the concentration of H3PO4 solution for immersion on H3PO4 loading level were investigated. H3PO4 loading level was found an important factor on membrane conductivity. Incorporation of Sb0.2Sn0.8P2O7 in the PBI‐H3PO4 membrane resulted in greater membrane conductivities. In the single cell tests, the peak power density of the membrane electrode assembly (MEA) with the PBI‐Sb0.2Sn0.8P2O7‐H3PO4 membrane was also greater than that of a MEA with PBI‐H3PO4 membrane. One MEA using PBI‐Sb0.2Sn0.8P2O7‐H3PO4 membrane achieved a peak power density of 0.67 W cm–2 at 175 °C with H2/O2 and exhibited satisfactory stability. 相似文献
10.
It is normal for a produced agricultural product or food to be transported to distances far from where it is produced. However, it is important to keep the product fresh in this transportation. There are many methods used to extend the life of the food during transport. The chemical method is the most used. However, the chemical method is harmful to human health. One of the methods used for storing, preserving and transporting agricultural products is ozonation and air conditioning. In this study, a system was designed to extend the life of the product in the storage and transport of food products. With the developed system, temperature, relative humidity and ozone were produced and their amounts were controlled according to the type of product being carried. In the design, polymer exchange membrane fuel cell was used for the required oxygen. The energy requirement of the system was provided by a photovoltaic panel to get rid of the generator dependency on supplied electrical power. The applicability of the system to refrigerated vehicles, especially those used in food transportation, was examined. 相似文献
11.
《Fuel Cells》2017,17(5):643-651
Membrane electrode assemblies (MEAs) were fabricated directly onto the electrolyte membrane, using an ultrasonic spraying technique. Pt–C catalysts, with concentrations of 10%, 20% and 40% by weight, were used, and the Pt loading onto the MEAs was kept constant at 0.3 mg cm−2. Nafion contents were considered from 15% to 35 wt.%. The morphologies of the MEAs were evaluated by scanning electron microscopy (SEM), in which the agglomeration of Pt–C particles was imaged, and a secondary pore in the catalyst layers (CLs) was revealed. The cross‐section images showed that the thickness of the CLs depended on the Pt–C concentration. The electrochemical surface area (ECSA) of those Pt–C concentrations and various compositions of Nafion contents were examined by cyclic voltammetry. Polarization curves were also measured and showed that the Nafion contents of 25 wt.%, 20 wt.%, and 15 wt.% gave the best performance for 10 wt.%, 20 wt.%, and 40 wt.% Pt–C catalysts, respectively. This indicates the Pt concentration is dependent on the Nafion content; the greater the weight of platinum in the catalysts, the less Nafion ionomer is required to optimize the electrochemical reaction. The data shows the same results regardless of the MEA fabrication techniques, operating conditions and Pt loadings. 相似文献
12.
Singaram Vengatesan Eunae Cho Hyoung-Juhn Kim Tae-Hoon Lim 《Korean Journal of Chemical Engineering》2009,26(3):679-684
To study the feasibility of applying solution-cast membranes to polymer electrolyte membrane fuel cells (PEMFCs), single cells prepared with solution-cast membranes were tested. The solution cast membranes were fabricated from a commercial Nafion solution under various conditions. Effects of annealing temperature on characteristics of the solution-cast membranes were investigated by measuring water uptake and ionic conductivity of the membranes. Performance of the single cells using the prepared solution cast membranes was evaluated in terms of i-V curves, Nyquist plots, and H2 crossover current density. Based on the results, solution-cast membranes were fabricated by being cured at 150 °C for different hours to examine effects of curing time on cell performance. Finally, durability of solution-cast membranes was investigated with operating the single cells for 1,000 hr. 相似文献
13.
《Fuel Cells》2017,17(6):794-808
Gas purge is commonly utilized to minimize residual water after shutdown of proton exchange membrane fuel cell (PEMFC) in cold weather, aiming to reduce damage of ice formation on cell performance and durability. In this paper, a three‐dimensional multiphase gas purge model of proton exchange membrane fuel cell with co‐flow and counter‐flow pattern is established to investigate water removal characteristics using two‐fluid model. The present model mainly includes water transport in membrane, mass transfer between dissolved water and water vapor in catalyst layer (CL), phase change between liquid water and water vapor in porous media. Several cases with co‐flow and counter‐flow pattern have been investigated numerically. In the last, gas purge time comparison between a fresh cell and degraded cell is conducted. The numerical results show that counter‐flow pattern is better in keeping even water content distribution and avoiding over‐drying of membrane. Time constant for gas purge is different in terms of different final target value: water vapor, liquid water saturation, membrane water content. Degraded cells have 2 more seconds than fresh cells when cell temperature is 80 °C and velocity of purge gas 1m s−1. 相似文献
14.
Composite membranes are prepared using sulfonated poly (arylene ether sulfone) (SPAES) copolymers and the incorporation of functionalized multiwall carbon nanotubes (CNTs) for high temperature (120 °C) proton exchange membrane fuel cells (PEMFCs). The CNT is functionalized with sulfonated groups that are expected to support the improvement of water absorption and mechanical properties. The SPAES copolymers are synthesized with sulfonation degree (DS) = 0.5 and the sulfonated CNT (s‐CNT) is dispersed into the SPAES copolymers in varying ratios to fabricate the composite membranes. In this study, the proton conductivity, water uptake, and single cell test of the composite membrane are investigated for verifying the effects of the enhancement at high temperature and low humidity. The composite membrane containing 0.2 wt.% s‐CNT increases proton conductivity approximately 45% at 120 °C and 50% relative humidity and enhances the tensile strength by about 1.3 times compared to the pristine membrane. However, the proton conductivity and water absorption shows a decline when more than 0.2 wt.% s‐CNT is added in the composite membrane, due to the aggregation of the s‐CNT, which serves as a proton barrier. For the single cell test, the developed composite membrane with 0.2 wt.% s‐CNT exhibits a notable performance for high temperature PEMFC. 相似文献
15.
High temperature PEMFCs based on phosphoric acid‐doped ABPBI membranes have been prepared and characterised. At 160 °C and ambient pressure fuel cell power densities of 300 mW cm–2 (with hydrogen and air as reactants) and 180 mW cm–2 (with simulated diesel reformate/air) have been achieved. The durability of these membrane electrode assemblies (MEAs) in the hydrogen/air mode of operation at different working conditions has been measured electrochemically and has been correlated to the cell resistivity, the phosphoric acid loss rate and the catalyst particle size. Under stationary conditions, a voltage loss of only –25 μV h–1 at a current density of 200 mA cm–2 has been deduced from a 1,000 h test. Under dynamic load changes or during start–stop cycling the degradation rate was significantly higher. Leaching of phosphoric acid from the cell was found to be very small and is not the main reason for the performance loss. Instead an important increase in the catalyst particle size was observed to occur during two long‐term experiments. At high gas flows of hydrogen and air ABPBI‐based MEAs can be operated at temperatures below 100 °C for several hours without a significant irreversible loss of cell performance and with only very little acid leaching. 相似文献
16.
《Fuel Cells》2018,18(4):413-421
Effect of freeze/thaw cycles on the performance of polymer electrolyte membrane fuel cell (PEMFC) is investigated. Freeze/thaw cycle is repeated 40 times. The performance is degraded, as the number of freeze/thaw cycles increases. The maximum degradation is about 35% at high current density. The performance degradation is analyzed based on the change of water distribution. X‐ray visualization is conducted 3 times; before, after 10th and 40th freeze/thaw cycle, respectivly. The water saturation in PEMFC is getting reduced, as the number of freeze/thaw cycles increases. Over‐potential analysis is conducted using visualization result by calculating the proton conductivity. The proton conductivity is decreased about 30% at high current density after 40th freeze/thaw cycle. The change of water distribution is analyzed based on the structural change of the GDL. The water volume change upon freeze/thaw cycle leads to cracks in the micro porous layer. It facilitates water removal from the GDL and leads to low water saturation in PEMFC. 相似文献
17.
Sulfonated poly(arylene ether sulfone) membranes based on biphenol for direct methanol fuel cells 总被引：1，自引：0，他引：1
Se Joon Im Rajkumar Patel Se Jong Shin Jong Hak Kim Byoung Ryul Min 《Korean Journal of Chemical Engineering》2008,25(4):732-737
A series of sulfonated poly(arylene ether sulfone) (PAES) were synthesized through direct aromatic nucleophilic substitution polycondensation of 3,3′-disulfonate-4,4′-dichlorodiphenylsulfone (SDCDPS), 4,4-dichlorodiphenylsulfone (DCDPS) and 4,4-biphenol (BP). With increasing sulfonate groups in the polymer, water uptake, ion exchange capacity (IEC) and proton conductivities increased, resulting from enhanced membrane hydrophilicity. The membranes exhibited higher thermal stability up to 300 °C, verified by thermogravimetric analysis (TGA). A maximum proton conductivity of 0.11 S/cm at 50 mol% of sulfonation degree was measured at 30 °C, which is slightly higher than Nafion®117 membrane (0.0908 S/cm). However, the methanol permeability of the PAES membrane was much lower than that of Nafion®117 membrane. As a result, a single cell performance test demonstrated that PAES-BP with 50 mol% sulfonation degree exhibited higher power density than Nafion®117. 相似文献
18.
T. Z. Fu J. Liu Z. M. Cui J. Ni G. Zhang H. B. Yu C. J. Zhao Y. H. Shi H. Na W. Xing 《Fuel Cells》2009,9(5):570-578
The sulphonated phenol novolac (PNBS) which was used as a curing agent of epoxy was synthesised from phenol novolac (PN) and 1, 4‐butane sultone and confirmed by FTIR and 1H NMR. The degree of sulphonation (DS) in PNBS was calculated by 1H NMR. The semi‐IPN membranes composed of sulphonated tetramethyl poly(ether ether ketone) (STMPEEK) (the value of ion exchange capacity is 2.01 meq g–1), epoxy (TMBP) and PNBS were successfully prepared. The semi‐IPN membranes showed high thermal properties which were measured by differential scanning calorimeter (DSC) and thermogravimetric analyses (TGA). With the introduction of the cross‐linked TMBP/PNBS, the mechanical properties, dimensional stability, methanol resistance and oxidative stability of the membranes were improved in comparison to the pristine STMPEEK membrane. Although the proton conductivities of the semi‐IPN membranes were lower than those of the pristine STMPEEK membrane, the higher selectivity defined as the ratio of the proton conductivity to methanol permeability was obtained from the STMPEEK/TMBP/PNBS‐14 semi‐IPN membrane. The results indicated that the semi‐IPN membranes could be promising candidates for usage as proton exchange membranes in direct methanol fuel cells (DMFCs). 相似文献
19.
《Fuel Cells》2018,18(2):103-112
The durability of high‐temperature polymer electrolyte membrane fuel cells (HT‐PEMFCs) was studied with phosphoric acid doped membranes of polybenzimidazole (PBI). One of the challenges for this technology is the loss and instability of phosphoric acid resulting in performance degradation after long‐term operation. The effect of the gas diffusion layers (GDL) on acid loss was studied. Four different commercially available GDLs were subjected to passive ex situ acid uptake by capillary forces and the acid distribution mapped over the cross‐section. Materials with an apparent fine structure made from carbon black took up much more acid than materials with a more coarse apparent structure made from graphitized carbon. The same trend was evident from thermally accelerated fuel cell tests at 180 °C under constant load where degradation rates depended strongly on the choice of GDL material, especially on the cathode side. Acid was collected from the fuel cell exhaust at rates clearly correlated to the fuel cell degradation rates, but amounted to less than 6% of the total acid content in the cell even after significant degradation. Long‐term durability of more than 5,500 h with a degradation rate of 12 µV h−1 at 180 °C and 200 mA cm−2 was demonstrated with the GDL that retained acid most efficiently. 相似文献
20.
The development of low cost alkaline anion solid exchange membranes requires high ionic conductivity, low liquid uptake, strong mechanical properties and chemical stability. PVA/PSSA blends cross‐linked with glutaraldehyde and decorated with titanium dioxide nanoparticles introduce advantages relative to the pristine membrane of PVA and PVA/PVP membranes due to their improved electrical response and low methanol uptake/ swelling ratio allowing their use in alkaline direct methanol fuel cells. 相似文献