Self-assembly Of Amino Acid Small Molecule Organogels And Their Composite Proton Exchange Membranes

Energy shortage has become one of the most serious problems in the world,the proton exchange membrane fuel cell(PEMFC)has attracted wide attention because of its low emissions,portability,and high energy density.As the core of PEMFC,the proton exchange membrane(PEM)should have good proton conductivity,alcohol resistance and chemical stability.However,commercial Nafion membranes have limited further wide application due to their high cost and low proton conductivity at high temperatures.The development of PEM with better performance has become a research focus in the field.In recent years,the use of nanofibers with high specific surface area and large aspect ratio to construct proton transfer channels has become an important method to improve proton conductivity.Inspired by the mechanism of proton conduction in natural organisms,this thesis uses the self-assembly characteristics of amino acid-based small molecule organogels to propose a research idea of constructing amino acid self-assembled nanofiber proton transport channels.The main research contents are as follows:First,the self-assembly law of phenylalanine(Phe)in different solvents was studied.Experimental observation and simulation calculations confirmed that the n-propanol/water mixed solution is more conducive to Phe self-assembly and proton transfer;solution jet spinning The nylon 6(PA6)nanofiber web was spun by silk technology,and Phe was self-assembled in the PA6 nanofiber web to prepare the Phe-PA6 multi-level composite nanofiber web,and then the Phe-PA6-Nafion composite proton exchange membrane was prepared.The test results show that the introduction of Phe-PA6 composite nanofibers effectively improves the water absorption of the proton exchange membrane,and its skeleton function effectively controls the swelling of the composite membrane and improves its dimensional stability.The self-assembled Phe nanofibers construct a regular proton transfer path so that the Phe-PA6-Nafion composite membrane has better proton conductivity than the Nafion membrane,and its proton conductivity reaches 0.241S/cm at 100% RH and 100?.The paper further studied the composite membrane with excellent proton conductivity under high temperature and low humidity,through the self-assembly law of L-cystine derivative N,N'-dibenzoyl-L-cystine(DBC)Research,make it perform one-step self-assembly in Nafion solution,and prepare DBC-Nafion proton exchange membrane.Through the moisture absorption and water retention of DBC gel,the water absorption and water retention of DBC-Nafion composite membrane are effectively improved,and the long-range order is used.The proton transfer channels of amino acids and self-assembled fibers promote polymer proton conduction under low humidity conditions,which effectively improves the proton conductivity of Nafion membrane under high temperature and low humidity conditions.The proton conductivity of DBC-Nafion-9 reaches 0.117S/cm at 100? and 60% RH,which is four times higher than that of Nafion membrane;DBC-Nafion-3 still maintains0.096S/cm at 120? and 60% RH.The proton conductivity of cm is more than 8 times higher than that of Nafion membrane.