Construction Of Transport Channels In Fuel Cell Composite Proton Exchange Membrane And Optimization Of Comprehensive Membrane Performance

Proton exchange membrane fuel cell（PEMFC）has the advantages of high energy conversion efficiency,environmental friendliness and wide range of fuel sources,which has attracted extensive attention from researchers.Proton exchange membranes（PEMs）as the core component directly affect the performance and operation life of PEMFC.At present,the Nafion^? membrane which is widely applied in the market,has excellent chemical stability and thermal stability,but its production process is complicated and costly.In the high temperature and low humidity environment,the proton transfer channel is remarkably compressed,resulting in a rapid decline in proton conductivity.Therefore,it is crucial to prepare cost-effective PEMs with high performance.This study focuses on the construction of proton transmission channels and the optimization of water environment in the membranes,acid-base double-shell carbon nanotubes（CNTs-C@N）and inorganic proton conductor functionalized halloysite nanotubes（BPO₄@DHNTs）were prepared respectively.The nano-composite PEM was synthesized via doping the nanofillers into Sulfonated poly（ether ether ketone）（SPEEK）matrix.Starting from constructing proton transmission channels and optimizing the water environment in the membrane,the vehicular mechanism and the Grotthuss mechanism in the composite membranes are jointly strengthened to improve high proton conductivity in a low humidity environment.The main research contents are as follows:1.The hierarchical proton transmission pathway was constructed in composite membranes using CNTs-C@N as functional nanofillers.CNTs with acidic shell containing carboxylic acid groups and basic shell containing imidazole groups were sequentially introduced into the SPEEK matrix to prepare composite membranes.Two acid-base pairs can be formed between the imidazole group on the outer shell of CNTs-C@N with the-COOH group on the inner shell and the-SO₃H group on the SPEEK,providing hierarchical channel transport for proton transfer.When the doping amount is 1.0 wt%,the proton conductivity of the composite membrane at 80℃and 60%RH is 6.40×10^-3 S·cm^-1,which is 4.24 times that of the SPEEK membrane(1.51×10^-3 S·cm^-1).2.The proton transport process was optimized using BPO₄@DHNTs as functional proton carriers.BPO₄@DHNTs was assembled by BPO₄ and HNTs using a polydopamine assisted sol-gel method,which were added to the SPEEK matrix to prepare composite membranes.BPO₄@DHNTs can bind more water in the composite membrane by utilizing the abundant hydroxyl groups on its surface and the cavity structure inside the HNTs,so that the composite membrane can still peform good proton conductivity at low humidity.In addition,BPO₄@DHNTs can bridge more water molecule clusters to form new transport channels and facilitate proton transport.When the doping amount is 7.5 wt%,the horizontal proton conductivity is 0.308 S·cm^-1 at 80°C under fully hydrated conditions,which is close to 2.54 times that of the SPEEK membrane(0.121 S·cm^-1).