| The sulfonated aromatic polymer membranes for all-vanadium redox flow battery application are faced a chanllenge to improve the chemical stability and balance its proton conductivity and vanadium permeability.For this problem,the functionalized carbon nanomaterials are introduced into SPEEK matrix to improve its physicochemical environment,construct effective ion transport channel,and fabricate high-performance and low-cost SPEEK hybrid membranes.This work provides a theoretical basis and technical route for development of sulfonated aromatic polymer membrane.The research contents of this paper are as follows:?1?The polydopamine-decorated carbon nanotubes?CNTs@PDA?as the interfacial modifiers are introduced into SPEEK matrix obtained SPEEK/CNTs@PDA hybrid membrane.The formed acid-base pairs between—NH2?—NH—groups of CNTs@PDA and—SO3H groups of SPEEK matrix effectively reduce vanadium ion permeability and increase the ion selectivity of SPEEK/CNTs@PDA hybrid membrane.SPEEK/CNTs@PDA-1 hybrid membrane shows the highest ion selectivity(17.3?103 S min cm-3).At 50 m A cm-2,the single cell aseembled with SPEEK/CNTs@PDA-1 hybrid membrane exhibits the higher coulombic efficiency?94.7%vs 94.0%?and energy efficiency?85.9%vs 83.5%?than that of Nafion 117memebrane.The 100 charge-discharge cycles and chemical stability tests show that the SPEEK/CNTs@PDA hybrid membrane has good cycling stability and chemical stability.?2?The DCNTs-HPW nanofillers are preparaed by loading phosphotungstic acid?HPW?on CNTs@PDA.The introduction of highly acidic HPW significantly improves the proton conductivity and ion selectivity of the SPEEK/DCNTs-HPW hubrid membrane.At 50 m A cm-2,the single cell aseembled with SPEEK/DCNTs-HPW-1 hybrid membrane exhibits higher coulombic efficiency?98.2%vs 94.7%?and energy efficiency?89.5%vs 85.9%?than that of SPEEK/CNTs@PDA hybrid membrane.However,the chemical stability of SPEEK/DCNTs-HPW hybrid membrane is inferior to that of SPEEK/CNTs@PDA hybrid membrane.?3?The amino functionalized graphene oxide?AGO?nanofillers with different alkyl chain length are preparaed by thermalsolvent reaction and amide reaction.The effect of the alkyl chain length and its additive amount on the performance of SPEEK/AGO hybrid membranes is investigated.EDA-GO nanofillers containing C2alkyl chain can significantly improve the proton conductivity and ion selectivity of hybried membrane with less addition.The proton conductivity and ion selectivity of SPEEK/EDA-GO-1 hybrid membrane are 26.5 m S cm-1 and 24.8?103 S min cm-3,respectively,which both are higher than the highest proton conductivity and ion selectivity of SPEEK/NH2-GO and SPEEK/HMD-GO hybrid membranes.The single cell assembled with SPEEK/EDA-GO-1 shows the highest energy efficiency?88.5%vs 84.9%and 87.7%?compared with that assembled with SPEEK/NH2-GO and SPEEK/HMD-GO hybrid membranes.However,EDA-GO nanofillers do not improve the chemical stability of the hybid membrane as much as NH2-GO and HMD-GO.?4?The zwitterions-decorated graphene oxide?ZC-GO?nanofillers containing amino and sulfonic acid group are prepared by two-step reaction.The introduction of ZC-GO nanofiller significantly improves the proton conductivity of SPEEK/Z-GO hybrid membrane,making the hybrid membrane exhibit an ultra-high ion selectivity.The proton conductivity and ion selectivity of SPEEK/ZC-GO-2 hybrid membrane are33.0 m S cm-1and 26.0?103S min cm-3,respectively.At the 50 m A cm-2,the energy efficiency of single cell assembled with SPEEK/ZC-GO-1 hybrid membrane is up to91.4%.A comprehensive comparison is conducted about the effects of CNTs@PDA,DCNTs-HPW,AGO and ZC-GO nanofillers on the performance of SPEEK-base hybrid membrane.The result shows that ZC-GO nanofillers can significantly improve the proton conductivity,ion selectivity and chemical stability of hybrid membranes,and the hybrid membrane shows the highest energy efficiency in the single cell test.And ZC-GO nanfiller is an ideal choice to improve the performance of sulfonated aromatic polymer membranes. |
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