Preparation And Properties Of Proton Exchange Membrane With Ionic Liquid Modified Graphene Oxide

The proton exchange membrane（PEM）is one of the core components of the proton exchange membrane fuel cell（PEMFC）.The main PEMs applied at this stage are perfluorosulfonic acid membranes（PFSA）such as Nafion,but Nafion membranes have disadvantages such as relatively high application cost,high fuel crossover and excessive dependence on water for proton transfer.In order to improve proton conductivity,different ionic liquids were designed.IL can provide new proton transfer sites in PEM applications.However,ionic liquids are easy to be lost in speek membranes.In order to solve this problem,inorganic nano materials go were introduced.Go and functional molecules can synthesize composites with special functions through hydrogen bonds,covalent bonds,Ï€-Ï€interactions and electrostatic interactions.Il was confined to speek membrane by using the different effects between IL and go.Meanwhile,the interaction of the two can improve the mechanical properties and dimensional stability of PEM,thus preparing PEM with excellent performance.Finally,the prepared nanomaterials and PEMs were analyzed by characterization and testing means.The main studies are as follows.（1）The solution casting method was used to dope both triethylamine phosphate（TEAP）and GO into the SPEEK substrate film,and the TEAP was anchored to the SPEEK substrate by the hydrogen bonding between TEAP and GO and the nano-constraining effect formed between GO and SPEEK.First,more proton transfer sites are provided through TEAP.Then,GO was inserted into the composite membrane to build a continuous proton transfer channel to increase the proton conductivity of the composite membrane,and GO provided a certain support skeleton to make the composite membrane have a good water absorption rate and better dimensional stability.Finally,the analysis of the study revealed that the composite membrane with TEAP and GO acting together had a lower IL loss rate,and the proton conductivity of the SPEEK/AIL/GO-2 membrane reached 17.34 m S cm^-1at 120℃.（2）The loss of IL is slowed down by adsorbing IL to the GO surface in a non-covalent interaction between IL and GO.We successfully prepared3-（3-sulfo）propyl benzothiazole dihydrogen phosphate（[（CH₂）₃SO₃HBth][H₂PO₄]）ionic liquid.and combine it with GO via cation-Ï€interaction to obtain IL-adsorbed GO（IL-GO）.The IL can act as both an acceptor and a donor for protons,freeing proton transport at high temperatures from the bondage of water.The study analysis concluded that the IL-GO modified composite membrane has good mechanical properties,where the elastic modulus of the SPEEK/IL-GO-2 membrane is 1.39 times higher than that of the SPEEK membrane.And the proton conductivity of SPEEK/IL-GO-2 membrane is 2.43 times higher than that of SPEEK membrane at120℃,which is a large improvement.（3）A stepwise functionalization method was used to bind IL to GO by covalent grafting,which prevented the loss of IL.The bis-imidazole cation was grafted to the carboxyl group on GO by chlorination,and then the phosphotungstic acid anion was introduced into it to obtain the double cationic liquid grafted GO（DIL@GO）.The imidazole cation forms acid-base pairs with-SO₃H on SPEEK as low-energy barrier channels along the channel surface,and the continuous path ensures efficient transfer of protons as they pass through these transfer sites.Finally,it was shown that the thermal stability and mechanical properties of the composite membranes containing DIL@GO were better,and the proton conductivity of all composite membranes was higher than that of SPEEK membranes,with SPEEK/DIL@GO-3 membranes reaching a conductivity of 19.61 m S cm^-1at 120℃.