The Study On Preparation And Properties Of Acid-base High Temperature Proton Exchange Membrane Modified By Pvp

As the core components of the Proton exchange membrane fuel cells(PEMFCs), proton exchange membrane(PEM) could insulate fuels and oxidants,conduct protons and insulate electrons,thus PEM could affect the properties of PEMFC directly. Nafion, the currently most widely used PEM, has excellent proton conductivity and mechanical properties under high relative humidity at low temperature. However, the application of Nafion has been restricted by its disadvantages such as complex water and heat management problem, extreme dependence on water, CO catalyst poisoning and high prices. Thus it's quite significant to develop a new kind of PEM for high temperature full cells. The phosphonic acid group has slightly lower ionization degree than sulfonic acid group, and could provide protons by self-ionization under low relative humidity at high temperature. Besides, phosphonic acid group has high hydroscopicity. Therefore, the PEM using phosphonic acid as proton carrier has been one of the hottest researches in PEM for high temperature full cells.In this essay, we prepared acid-base proton exchange membranes and their PVP modifying membranes by using amino trimethylene phosphonic acid(ATMP) as proton carrier, aminopropyltriethoxysilane(APTES) as precursor, and polyvinylpyrrolidone(PVP) as modifier. Two kinds of memberanes were both prepared by sol-gel process in distilled water. We expected PVP could form stable coordination complexes with amino siloxane phosphonates to promote PEM's chemical and mechanical stability and that carbonyl group in PVP could form hydrogen bond with hydroxyl in membranes. It's also expected the introduction of N could promote synergistic effect between N and P in membranes to accelerate self-ionization of phosphonic acid to promote the formation of proton transferring channel.FT-IR analysis confirms acid-base neutralization reaction occurred between phosphonic acid group in ATMP and amino in APTES, creating acid-base ion pairs. Meanwhile, Si-O-Si network structure has been formed by the hydrolysis reaction of amino siloxane. XRD study shows the amorphous nature of membranes. TG-DSC analysis reveals two kinds of membranes showed good thermal stability and could operate within 200?. The hydrolysis resistance, water absorption, swelling degree and oxidation resistance test results indicate the introduction of PVP have improved the hydrolysis resistance, water absorption, dimensional stability and oxidation resistance of acid-base membranes. Morphology analysis shows there are no apparent phase separation and agglomeration in the surface and section of PVP modified membranes, indicating PVP has a good consistency with proton membrane. It also reveals the addition of PVP has made the structure of membrane more compact, improving membrane's water absorption and retention. Two kinds of membranes showed good proton conductivity under low relative humidity at high temperature. The ion exchange capacity(IEC) and proton conductivity test analysis indicates that proton conductivity of membranes were improved by the increase of IEC and the addition amount of PVP,for instance,the acid-base membrane AAM-1 get a proton conductivity of 1.64 × 10- 2 S · cm- 1at 140 ?,while its PVP modified membrane AAMP-2 reached 1.73×10-2 S·cm-1, indicating the introduction of PVP accelerated the self-ionization of phosphonic acid and promoted the formation of proton transferring channel.