Preparation And Properties Of Nitrogen Heterocyclic Grafted Sulfonated Poly (Arylene Ether Ketone Sulfone) Proton Exchange Membranes

Proton exchange membrane is the core component of proton exchange membrane fuel cell.It has the function of transmitting protons and blocking fuel and oxidant.Its performance directly affects the application of proton exchange membrane fuel cells.At present,the most widely used proton exchange membrane is the commercial Nafion perfluorosulfonic acid membrane produced by DuPont,which is highly favored for its excellent proton conductivity,chemical stability and mechanical properties.However,the high cost and high methanol permeability hinder the further development and application of the Nafion membrane.Therefore,the search for a polymer material capable of replacing the Nafion membrane has been the main research direction.Sulfonated poly?arylene ether ketone sulfone?s is an excellent engineering material with excellent thermal stability,chemical stability and low price,making it the most potential alternative to Nafion.However,when the temperature of the proton exchange membrane is higher than 80?the water in the system is quickly lost,and the decrease of the proton carrier directly affects the proton conductivity of the membrane.And the proton transfer is the same as the methanol permeation route,so the high proton conductivity is often accompanied by the problem of high methanol permeability coefficient.Researchers want to create a proton transport channel that does not rely on water,hoping to break the limits between proton conductivity and methanol permeability and get rid of the dependence of protons on water.Firstly,a sulfonated polyarylether ketone sulfone polymer containing a carboxyl group was prepared,and then 4-aminopyridine was immobilized on the polymer chain by grafting.It is hoped that the dense structure after grafting can effectively reduce methanol.The infiltration,while utilizing the properties of proton conductors and acceptors with nitrogen heterocycles,constructs a new proton transport pathway that only transmits protons.It was found by experiments that the methanol permeability coefficient of the membrane decreased significantly from 8.17×10^-7cm²s^-11 to 8.92×10^-8cm²s^-11 at 25?as the amount of pyridine grafting increased.The proton conductivity and relative selectivity of the membrane were positively correlated with the grafted pyridine content.Among them,the SPP-4 membrane had the highest proton conductivity at 100?,which was 0.088 S cm^-1.In order to further improve the proton conductivity of the membrane under medium and high temperature conditions,we chose 5-aminotetrazole as a new graft.Since5-aminotetrazole?8.1?has a smaller PKa value than 4-aminopyridine?9.114?,the degree of dissociation is higher,and a higher degree of dissociation reduces the solvent effect and makes proton migration easier.And there are 4 N atoms on the 5-aminotetrazole ring,which will provide more jumping sites for the transfer of protons.Compared with the SPP-y membrane,it was found that the SPAT-4 membrane had a proton conductivity of up to 0.0933 S cm^-11 at 100?,which was significantly higher than that of the SPP-4 membrane,and had higher relative selectivity.