Preparation And Characterization Of Thiazole And Pyrrolidine Quaternized Hydroxide Exchange Membrane

Hydroxyl ion exchange membrane fuel cell is a new kind of fuel cells, which has a lot of advantages. Compared with proton exchange membrane fuel cells, its electrode reaction rate is faster, the cost of preparation is lower, non-noble metal can be used as catalyst and so on. Hydroxyl ion exchange membrane which is the core components of fuel cell, plays the role of conducting hydroxyl ions and separating the cathode and anode compartments. Besides, the performance and service life of fuel cells are determined directly by the membranes.The low conductivity of hydroxyl ion and poor stability of ionic conduction groups are the key problems of hydroxyl ion exchange membrane that need to be improved. In this paper, thiazole and 1-methylpyrrolidine were used as quaternary ammonium groups, polyether-ether-ketone(PEEK) and polyether sulphone(PES) were used as basis materials, and Thiazole and Pyrrolidine quatemized PEEK and PES hydroxyl ion exchange membranes were prepared successfully.Firstly, thiazole was chosen as quaternary ammonium groups, Solution-casting method was used to prepare PEEK-ThOH and PES-ThOH. And then series of membranes were tested, the results were follows:when IEC was in the range of 0.48 mmol/g-1.13mmol/g, the water absorption rate of PES-ThOH was moderate. PES-ThOH (IEC was 1.26mmol/g) had a high water absorption rate that make conductivity of hydroxide ion reach the highest value (41.7mS cm-1).The water absorption rate of PEEK-ThOH was slightly increased compared to PES-ThOH. The PEEK-ThOH (IEC was in the range of 0.88 mmol/g-1.56mmol/g) had good water absorption and moderate swelling degree, hydroxyl ion conductivity of PEEK-ThOH (IEC was 1.78mmol/g) grew slowly at 60℃,but reached 50.3mS cm-1.Besides, the initial decomposition temperature of PES-ThOH was 161 ℃, which was slightly better than PEEK-ThOH. PEEK-ThOH and PES-ThOH showed good chemical stability,which deteriorated at 30-60 ℃,but chemical stability of PES-ThOH was slightly better than PEEK-ThOH.In order to further improve the hydroxyl ion conductivity of membrane 1-methylpyrrolidine was used as quaternary ammonium groups. PEEK-PyOH and PES-PyOH were prepared in the same way, the results were follows:The quaternization degrees of PEEK-PyOH and PES-PyOH were all improved compared to PEEK-ThOH and PES-ThOH, as a result, the amount of Ionic conduction group increased, therefore the water absorption and hydroxyl ions conductivity were improved as well. When the temperature reached 60 ℃, PES-PyOH (IEC was 1.48mmol/g) dissolved in water due to excessive absorption, Hydroxyl ions conductivity of PES-PyOH (IEC was 1.21mmol/g) reached the highest value that was 48.6mS/cm at 60℃. At room temperature, the water uptake increased from 38.2% to 152.3% as the IEC increased from 0.96mmol/g to 2.07mmol/g for PEEK-PyOH. The hydroxyl ions conductivity was 36.8mS cm-1 at room temperature and 53.5mS/cm at 50℃ which was the highest value when IEC of the PEEK-PyOH was 2.07mmol/g. Besides, the initial decomposition temperature (248℃) of PES-PyOH was higher than that (115℃) of PEEK-PyOH, as the temperature changed,variation of chemical stability of PEEK-PyOH and PES-PyOH was consistent with PEEK-ThOH and PES-ThOH. However, chemical stability of PEEK-PyOH and PES-PyOH was a little less than PEEK-ThOH and PES-ThOH.