Preparation And Study Of Acid-base High Temperature Proton Exchange Membrane Made From Phosphonic Acid

Fuel cell is a truly environmentally friendly new energy,which will not discharge any pollutants such as waste gas to the environment.Proton exchange membrane fuel cell?PEMFC?is considered to be one of the most promising electrochemical energy conversion devices for its outstanding properties,such as fast initiation and high power density.The proton exchange membrane?PEM?is the crucial component of PEMFC,which directly determines the performance of PEMFC.At present,the commercial one is Nafion.It cannot work in the high temperature and low humidity environment as the proton conduction strongly depends on water.Besides,there are some other factors to prevent Nafion from widely applying and developing like cumbersome preparation process and high cost.A new type of PEM which possesses high proton conductivity under high temperature and low relative humidity condition with lower cost has been required.In this paper,two kinds of acid-base high temperature proton exchange membranes by using aminotrimethylenephosphonic acid?ATMP?as proton conducting unit were prepared and analyzed,as follows:?1?One kind of acid-base high temperature proton exchange membrane was prepared from ATMP,epoxycyclohexyethyltrimethoxysilane?EHTMS?,and3-aminopropyltriethoxysilane?APTES?by sol-gel process.The EHTMS and APTES were chemically bonded to ATMP by epoxy ring opening reaction and acid-base neutralization reaction with ATMP as the main proton conducting unit.FTIR and XRD tests show that the chemical reaction is successful and the prepared proton film is amorphous.Besides,the membrane has good dimensional stability and thermal stability,can be stable before 200?.SEM results show that the microstructure of the membrane is homogeneous and compact,and no phase separation is observed.The IEC and the proton conductivity of the membrane increases with the increasing of APTES,and the proton conductivity is 2.63×10^-2 S·cm^–1 at 140?.The variable-temperature FTIR further proves the formation of hydrogen bond network.The formation of the acid-base pair can reduce the activation energy required for the proton conduction,provide another channel for the transmission of the proton which can cooperate with the hydrogen bond network to enhance the proton conductivity.?2?The acid-base high temperature proton exchange membrane was prepared by sol-gel process,and the chitosan was chemically bonded to the ATMP/APTES/EHTMS system through acid-base reaction.FTIR and XRD tests show that the amino groups on chitosan are successfully protonated.The thermal stability,physicochemical stability and mechanical properties of the membrane were characterized.The result shows that the membrane has thermal excellent stability and physical stability.Also,the chemical stability and mechanical properties of the membrane are obviously improved compared with the ATMP/APTES/EHTMS membrane,which can meet the performance requirements during assembly and long term use.In addition,the microstructure of the membrane shows good uniformity,and no through-hole and phase separation can be observed.When the test temperature reaches 140?,the membrane has an anhydrous proton conductivity of 3.4×10^-2S·cm^–1,which can meet the requirements of high temperature and low humidity environment.