Preparation Of Highly Conductive And Robust Proton Exchange Membrane And Proton Transfer Mechanism Investigation

The development of highly conductive and robust proton exchange membrane is ungently needed in proton exchange membrane fuel cell.However,restricted by the trade-off effect between proton conductivity and structural stability and it is difficult to improve the proton conductivity and structural stability simultaneously.In addition,traditional Grotthuss and Vehicle mechanism restrict structural design of high-performance proton exchange membranes due to the lack of effective interaction with the proton transfer channel microenvironment.In this paper,control of microstructure and interaction at molecular level was adopted to prepare highly conductive and robust proton exchange membranes and synergically improved the proton conductivity and structural stability,and proposed the proton transfer mechanism in long range and ordered ionic channel.The main research results are as follows:Preparation of highly conductive and robust polymer quantum dot membrane by bionic complexation.Inspired by the complexation of the super binder secreted by the natural saltworm,polymer quantum dots（PQD）and sulfonated polyether ether ketone（SPEEK）were used to prepare dense PQD membrane by solvent osmotic complexation method.The electrostatic complexation generated between sulfonic acid groups of SPEEK and amide groups of PQD conferred the membrane with promoted mechanical strength for more than 4-5 times.The phosphoric acid,sulfonic acid groups in the PQD formed a continuous proton transfer channel and proton conduction process was intensfied.The proton conductivity reached 264 m S cm^-1 at80℃under 100%relative humidity.Control of edge and in-plane interaction toward highly conductive and robust GO membrane.Herein,sulfonated graphene quantum dots（SGQD）were prepared and intercalated into GO layers to control the edge electrostatic interaction and in-planeπ-πinteraction of SGQD with GO nanosheets.Three electron withdrawing groups were employed to modulate the edge electrostatic interactions between SGQD and GO to improve the water swelling resistant property of GO membranes.Meanwhile,SGQD with abundant proton donor groups assembled on the sp² domain of GO via in-planeπ-πinteraction and confered the GO membranes with low-energy-barrier proton transport channels.As a result,the GO membrane achieved an enhanced proton conductivity of 324 m S cm^-1 at 75 ^oC under 100%RH.De nove design and preparation of highly conductive and robust covalent organic framework membrane and proton transfer mechanism investigation.In this study,ionic covalent organic framework（COF）membrane was de nove designed and prepared.The in-plane covalent interaction andπ-πinteraction between COF nanosheets was utilized to improve the structural stability of the membrane,and the proton transport process was intensified with the aid of regular proton transfer channels.By controlling the COF monomer structure,the group distance was modulated and the delocalization drivern proton transport mechanism was investigated.The results indicated that when the sulfonic acid groups distance reduced to 1-1.4 nm,the delocalization driven proton transport effect were significantly enhanced,and the highest proton conductivity reached 1389 m S cm^-1 at 90 ^oC under100%relative humidity.Preparation of highly conductive and robust phosphoric acid loaded COF membrane by control of multiple interactions.In this study,a series of phosphoric acid loaded covalent organic framework membrane with quaternary ammonium groups were de nove designed and prepared.Based on the well-ordered pore structure of COF,the proton transfer process was intensified.The strong electrostatic interaction between phosphoric acid and quaternary ammonium groups and theπ-πinteraction between COF nanosheets promoted the proton conductivity and structure stability.The results indicated that the trimethyl quaternary ammonium group bearing small size,which generated weak influence on theπ-πinteraction between COF nanosheets,and the membrane exhibited superior structural stability.The PA loaded QACOF membrane achieved a proton conductivity of 379 m S cm^-1 at 200℃and exhibited better proton conductivity stability.