The Preparation And Characterizations Of PAM/SA-H₃PO₄ High-temperature Proton Exchange Membrane

Energy crisis and environmental problems have become increasingly prominent, new energy technologies become the key to solve these problems. The working temperature of high temperature proton exchange membrane fuel cell (HT-PEMFC) is between 100 ℃ and 200 ℃, which it’s chemical reaction kinetics are faster; It simplifies water management system; It is more efficient on thermal management and has better environmental tolerance. These advantages make the high temperature proton exchange membrane fuel cell has more attention. Proton exchange membrane (PEM) is a key component in a PEM fuel cell.Here we employed acrylamide and sodium alginate as reactants by a solution polymerization method to produce the graft copolymerization polyacrylamide/sodium alginate gel proton exchange membrane. And initiator is ammonium persulfate (APS), crosslinker is N,N’-(methylene) bisacrylamide (NMBA). The PAAm-g-SA membranes were immersed in H3PO4 aqueous solution to reach absorption equilibrium, then we will obtain the H3PO4 incorporated PAAm-g-SA membranes.The morphologies of the porous structures were captured with a zeiss emission scanning electron microscopy (SEM) and fourier transform infrared spectrometry spectra (FTIR). The results show that PAAm-g-SA membranes are 3D framework. The anhydrous H3PO4 can be sealed in the 3D framework. The change of absorption bands suggests that H3PO4 molecules interact with PAAm-g-SA to form hydrogen bonds. The formation of these hydrogen bonds plays an important role in the conductivity behavior of the membranes.The proton conductivity of the H3PO4 incorporated PAAm-g-SA membranes were characterized with ac-impedance spectroscopy using a CHI660E Electrochemical Workstation. The results show that the protons transfer migrating across hydrogen bonds present in H3PO4 as well as those formed between H3PO4 molecules and functional groups such as C=O,-NH2, P=O and C-O in PAAm-g-SA. Proton conductivity is highly dependent on the H3PO4 loading, higher loading and therefore better proton conductivity. The proton conductivity can be better with higher temperature.The H3PO4 loading can be adjusted by changing the dosages of initiator and crosslinker. Here we discussed the best dosage of initiator and crosslinker, the results show that when the dosage of initiator was 0.03 g, H3PO4 loading could be up to 91.2 wt% and the proton conductivity was 0.017 s·cm-1; when the amount of crosslinker was 0.01 g and H3PO4 loading was 87.5 wt%, the proton conductivity was 0.090 S cm-1.Through testing the high temperature stability performance of the H3PO4 incorporated PAAm-g-SA membranes over 100 ℃, the results claimed proton conductivities can remain stable for a long time and ensure the conductivity in actual applications. Suggest that it is a good high-temperature PEM candidate for potential PEMFC applications,...