Fabrication Of Proton Exchange Membrane And Construction Of Proton Conducting Channels Based On Two-dimensional Materials

Fuel cell is a kind of clean and efficient device which presents great potential to solve the energy shortage and environmental pollution problems and realize the sustainable development.Proton exchange membrane fuel cells(PEMFCs)have the advantages of high power density,safety,portability and wide range of applications,which is one of the most promising and mature fuel cells.Proton exchange membrane(PEM)is the key component of PEMFCs.Its performance directly decides the performance of PEMFCs.Fabricating high performance PEM is the key process to enhance the efficiency of PEMFCs.This study uses intrinsic proton conductive two-dimensional(2D)materials as the building blocks.The membranes with continuous long range proton conducting channels are prepared via vacuum assisted self-assembly method.The DNA molecules have a large number of orderly arranged phosphate groups which can act as proton conducting sites.The DNA molecules introduced into the 2D channels to optimize the distribution of proton conducting sites,which enhances the continuous of the channels.The impact of the physical-chemical microenvironment of the proton conducting channels on the proton conducting process is investigated by changing the type of 2D materials and proton conducting sites.The main conclusions are summarized as follows:The DNA@GO-X membranes with continuous long range proton conducting channels are prepared via vacuum assisted self-assembly method,using the 2D graphene oxide(GO)sheets as the building blocks.DNA molecules assemble on the surface of GO sheets through pre-assemble method.The 2D GO sheets provide continuous ordered physical channels and DNA molecules with a large number of orderly arranged phosphate groups optimize the distribution of proton conducting sites in the channels.GO and DNA synergistically enhance proton conduction process in the channels,which improves the proton conductivity of DNA@GO-X membranes.The DNA@GO-3 membrane shows the highest proton conductivity of 568.4 mS cm^-1 at 80?,98%relative humidity,which is 4.4 times higher than that of the pristine GO membrane.DNA@GO-3 membrane presents the highest power density of 136.5 mW cm^-2 in the single fuel cell test and this value is 3 times higher than the power density of the pristine GO membrane.The 2D COF sheets with sulfonic acid groups and ordered structure are used as building blocks.The DNA@COF-X membranes are prepared via vacuum assisted self-assembly method.The sulfonic acid COF sheets have regular channels,laminar structure and vertical one dimensional channels,which offer favorable physical structure for constructing the proton conducting channels.The sulfonic acid groups on the COF skeleton and the orderly arranged phosphate groups of the DNA molecules further optimize the chemical microenvironment of the proton conducting channels in DNA@COF-X membranes.The proton conductivity of the pure COF membrane is305.3 mS cm^-1 at 80 ?,98%relative humidity.And the DNA@COF-3 membrane shows the highest proton conductivity among the as-prepared membranes under this condition,reaching to 494.7 mS cm^-1,which is 1.6 times higher than that of the pure COF membrane and 4-5 times higher than that of Nafion series membrane(?100 mS cm^-1).