Preparation And Properties Of Proton Exchange Membranes Based On Sulfonated Poly(ether Ether Ketone) And Its Nanocomposites

Direct methanol fuel cell?DMFC?is a novel proton exchange membrane fuel cell?PEMFC?with methanol as fuel.DMFC is regarded as one of the most promising clean energy,with the advantages of high efficiency,no pollution,etc.As one of the most important components of DMFC,proton exchange membrane?PEM?plays a decisive role in the operation of the fuel cell.However the widely used perfluorosulfonic acid?PFSA?membrane has some drawbacks of high cost and high methanol permeability,leading to the low energy conversion efficiency of DMFC.Therefore,it is necessary to develop sulfonated hydrocarbon fluorine-free polymer materials with low cost and low fuel permeability.Sulfonated poly?ether ether ketone??SPEEK?is a good proton exchange membrane materials with relatively high proton condu ctivity,perfect thermal stability,good mechanical properties and low price.The SPEEK membranes were prepared via solution casting using the ethanol/water mixed solvent,with higher proton conductivity than those cast from dimethylacetamide?DMAc?.The casting temperature was found to play an important role in determining the properties of cast membranes: the lower casting temperature facilitates the aggregation of hydrophilic domains and the enlargement of phase separation,meanwhile,promotes the preferential arrangement of sulfonic acid groups on the membrane surface,leading to the higher proton conductivity.First,functioned g-C₃N₄ nanosheets were prepared via the adsorption properties of poly dopamine and sodium dodecyl benzene sulfonate?SDBS?.Proton exchange composite membranes are fabricated by incorporating functioned g-C₃N₄ nanosheets into sulfonated SPEEK.The interface compatibility between g-C₃N₄ and SPEEK matrix was improved because of the hydrophilic groups on poly dopamine and SDBS,leading to better connectivity of the ionic groups,and triggering the acid-base pair effect,rendering more continuous pathways for protons.The composite membranes doped with modified g-C₃N₄ have improved conductivity.of.the g-C₃N₄ nanosheets could serve as methanol barriers.Because of g-C₃N₄ nanosheets polymer chain flow,methanol permeability decreased.The methanol permeability decreases as g-C₃N₄ nanoparticles block the flow of the polymer chains.The SPEEK/g-C₃N₄/SDBS composite membranes were prepared by blending homogeneous mixed solution of SDBS and g-C₃N₄ with the SPEEK casting solution.g-C₃N₄ were uniformly dispersed in SPEEK matrix.The interface compatibility between g-C₃N₄ and SPEEK matrix was improved,leading to better connectivity of the ionic groups,rendering more continuous pathways for protons.The proton conductivity of the composits membrane with 2 wt% g-C₃N₄ nanosheets was increased by 60% compared with the SPEEK membrane.