| With many advantages such as good power density, small noise and little or evennear-zero emissions and so on, proton exchange membrane fuel cells have become animportant approach for every country in the world to solve the environmental pollutionproblem. With small molecular hydrocarbons such as coal gas, natural gas as fuel, small fuelcell power plant used in household and office building on improving the efficiency of primaryenergy, prevention and control of atmospheric pollution and emissions of CO2and othergreenhouse gases is of great significance for such a country whose resource exhaustion andlow comprehensive utilization. However, with small molecule hydrocarbons as fuel, it isnecessary to set a reformation unit to convert them into H2before proton exchange membranefuel cell whose work temperature below80℃. This conversion process is usually companiedby CO deputy. CO will cause Pt and other precious metal catalyst poisoning and reduce itscell performance. So in order to ensure the efficient operation, reformed gas must be purifiedto10parts per million before it is imported into fuel cell, thus increasing fuel cell cost, sizeand complexity. When rising the operating temperature to above100℃gradually, on onehand, CO’s poisoning effect on precious metal catalyst is greatly abate, until harmless. On theother hand, the high temperature waste heat utilization efficiency have been greatly improved.Thus, research and development of middle-high temperature proton exchange membrane fuelcell for small-size home and office thermoelectric combined power generation device isbecoming a more optimal solution. And research and development of proton exchangemembrane materials for high temperature fuel cell becomes quite an important subject.Existing high temperature proton exchange membrane materials mainly has three types:(1) non-fluoride sulfonic acid membranes, such as sulfonated polyimides, with advantages oflow cost, suitable for high temperature operation and stable performance, but its disadvantageis that easy degradation and lower conductivity.(2) polymer/in-organic composite membrane,such as acid doped poly-benzimidazole composite film;(3) some solid acid, such as CsHSO4,CsH2PO4, etc. The last two classes got extensive research in recent years. Results showed thatthey had advantages of high proton conductivity under high temperature and low humidity,but complex preparation technology, expensive and poor stability under high temperature (80-120℃). So thinking in terms of economical, environmental protection, and stableperformance, research and development of non-fluoride sulfonic acid membranes withexcellent comprehensive performance under high temperature is still an important way to gethigh temperature proton exchange membrane materials.Poly(ether ether ketone)(PEEK) and poly (aryl ether sulfone)(PAES) are two commonthermoplastic engineering materials with more excellent comprehensive performance. Such asexcellent mechanical properties, good resistance, corrosion resistance, and so on. Especiallysuitable for continuous use under high temperature, and even temperature changes rapidly. Atpresent, PEEK and PAES products have penetrated into many areas. In addition, theirsulfonated products, an important direction on research and development of new protonexchange membrane materials in high temperature because of good thermal stability,chemical stability, and low price, attracted much attention of the scientific researchers.Based on the present situation, to develop electrolyte membrane materials suitable forhigh temperature and low price, with the proton exchange membrane materials for fuel cellsas the research background, based on the relationship of structure and performance andphysical and chemical properties of poly(arylene ether ketone sulfone) com-polymers, in thispaper we designed and synthesized a series of sulfonated poly(arylene ether ketone sulfone)com-polymers with different sulfonation degree. Then verified their structures and studiedmembrane properties and even single cell performances. And main parts as following.First part, synthesis of the sulfonated monomer.Prepared3,3’-disulfonic acid-4,4’-dichloro diphenyl sulfone (SDCDPS) sulfonatedmonomer by adopting a pot sulfonation method innovatively and successfully. Timely,prepared the sulfonated monomer with4,4’-dichloro diphenyl sulfone (DCDPS) as monomer,phosphorus pentoxide/sulfuric acid as sulfonation reagent. And verified its recrystallizationproduct structure by using infrared spectrum and hydrogen nuclear magnetic resonancespectrum. Results showed that introducing sulfonic group onto3、3’ sites of DCDPSsuccessfully, and phosphate generated by P2O5reaction with sulfuric acid had no influence onsulfonated product structure.Second part, synthesis and characterization of sulfonated poly (arylene ether ketonesulfone) polymers and their acid-form membrane preparation. By using sulfonated monomer direct polycondensation method, synthesized a series ofrandom sulfonated poly (arylene ether ketone sulfone) com-polymers with above SDCDPS assulfonated monomer, and4,4’-double fluorine phenyl ketone, adjacent tetramethyl bisphenolby the direct polycondensation method using above sulfonated monomer. And using nuclearmagnetic resonance hydrogen spectrum diagram and Fourier transformation infraredabsorption spectrogram verified their structures. Results showed that resulting polymers werejust the target polymers. Further more, we studied their solubility. And resulting polymersexhibited good solubility in N-Methyl Pyrrodione(NMP)at room temperature. With NMP assolvent, we used the solvent casting method to get the series of salt-form target polymermembranes, and acidified them with hydrochloric acid.Third part, study on properties of sulfonated poly (arylene ether ketone sulfone) polymermembranes.We studied on properties of sulfonated poly (arylene ether ketone sulfone) polymermembranes. At the same time, the corresponding performances were compared withNafion117purchased from the Du Pont limited company. The results showed that this seriesof polymer membranes not only exhibited excellent thermal stability, but also othermembrane properties, such as water up-take, swelling ratio and ion exchange capacity, protonconductivity and methanol permeability, mechanical properties and oxidation resistance, et al.changed with the increasing sulfonation degree regularly, due to the structural similarity andcomparability between the series of polymers. And results showed that the flexibility andoxidation resistance of poly (arylene ether ketone sulfone) with higher sulfonation degree(sulfonation degree is not less than0.8) were inferior to Nafion117, but their potentialapplication in high temperature proton exchange membrane fuel cell was still worthexploring.Forth part, single cell performance testing.Used the series of sulfonated poly (arylene ether ketone sulfone) acid-form polymermembranes as the electrolyte membranes to explore the direct methanol fuel cell single cellperformance. Thus prepared the membrane electrode assembly (MEA) with sulfonated poly(arylene ether ketone sulfone) acid-form polymer membrane to go on the direct methanol fuelcell single cell test. Testing results showed that the open circuit voltage of the low sulfonation degree (sulfonation degree is less than0.8) of acid-form polymer membrane electrodeassembly of fuel cells was around0.5v, near no discharging, and the battery power densitywas quite low, about0.10mW/cm2. When the sulfonation degree was greater than or equal to0.8, the open circuit voltage of the battery could reach0.8v at the temperature70℃, and theratio of discharging electricity was relatively stable, with the battery power density couldreach50mW/cm2. These results proved that higher sulfonation degree poly(arylene etherketone sulfone) polymer membranes were suitable to be used in low temperature protonexchange membrane fuel cells as the electrolyte membrane materials. |
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