Preparation And Properties Of Crosslinked Sulfonated Poly(Etheretherketone)Composite Proton Exchange Membranes

Proton exchange membrane fuel cell?PEMFC?is an electrochemical reaction device that converts chemical energy of fuel directly into electrical energy.It is environmentally friendly,has good stability and is easy to maintain.It is considered as the most promising new generation technology in modern times.The electrolyte and battery diaphragm of the fuel cell are particularly critical for the improvement and development of the whole battery performance.The proton exchange membrane?PEM?as the core material of fuel cell,which supports the catalyst layer and acts as a barrier between the anode and cathode,has a direct impact on the stability and durability of fuel cell.In order to achieve high efficiency and stability in fuel cell operation,the requirements that the proton exchange membrane must meet under the operating conditions of the fuel cell include high proton conductivity,stable mechanical properties,adequate chemical stability,low permeability,high power density and low cost during operation.These requirements have always been a key research issue in the field,and are also important for improving the performance of proton exchange membrane fuel cells.In this paper,proton exchange membrane was prepared by sulfonating polyether ether ketone and inorganic nanomaterials for PEMFC.In this work,self-crosslinked sulfonated polyether etherketone membrane?C-SPEEK?was synthesized by Friedel-Crafts alkylation at 130 ^oC after preparation of chloromethylated sulfonated polyether ether ketone?SPEEK-Cl?.The C-SPEEK had a water absorption rate of 47.75%and a swelling rate of 8.69%at 60 ^oC,compared with the sulfonated polyether ether ether ketone membrane?SPEEK?with a water absorption rate of 110.60%and a swelling rate of 57.99%.The contradiction between dimensional stability and proton conductivity under high sulfonation degree is overcome.The self-crosslinking doped composite membranes were prepared by adding carbon nanomaterials?graphene oxide GO,reduced graphene oxide rGO,sulfonated graphene oxide SGO and carbon nanotubes CNTs?and phosphotungstic acid?HPW?to the membrane solvent in a one-step process by means of physical blending.Since the HPW and carbon nanomaterials presented in membrane promote ion conduction through both Vehicle and Grotthuss mechanisms,the composite membranes exhibited better proton conductivities.Taking SPEEK/HPW/GO membrane as an example,its proton conductivities was as high as 119 mS/cm at 80°C,which is 2.4 times greater than that of the C-SPEEK.Moreover,the H₂/O₂ single cell test further confirmed the superior performance of the SPEEK/HPW/GO membrane.A higher power output of876.80 mW/cm² was generated with this composite membrane under the testing conditions,whereas only 776.72 mW/cm² for the C-SPEEK membrane.C-SPEEK and C-SPEEK/HPW/GO both have a maximum open-circuit pressurization of more than 0.9 V,among which the open-circuit voltage value of C-SPEEK/HPW/GO is 0.96 V,indicating that the addition of the composite membrane has excellent resistance to hydrogen and oxygen diffusion.Then,the crosslinked SPEEK-SGO proton exchange membrane was synthesized by click chemistry.In chapter 3,on the basis of synthesis of SPEEK-Cl,clickable alkynated sulfonated polyether ether ketone?SPEEK-CH₂N₃?was prepared by nucleophilic substitution.On the basis of SGO,the carboxyl group on sulfonated graphene was activated by the EDC/NHS activation system,and then the carboxyamine reaction with propargyne resulted in the preparation of a clicking alkynated-SGO?SGO-C?C?.The crosslinked SPEEK-SGO_X composite proton exchange membranes were prepared using clickable SGO as a crosslinking agent in the classic click-catalyzed systems of PMDETA and CuBr.The composite membranes showed excellent dimensional stability.The water absorption rate and swelling rate of the composite membranes at 60 ^oC were both lower than 13%and 7%respectively.SPEEK-SGO_0.5 not only showed excellent dimensional stability but also higher proton conductivity than C-SPEEK at 60 ^oC.In this paper,C-SPEEK doped with different carbon nanomaterials and phosphotungstic acid composite proton exchange membranes and SPEEK-SGO_X series composite proton exchange membranes were prepared.