Research On The Construction Of Amino Acid Clusters Based On Nanofibers And Their Proton Conduction Behavior

Proton exchange membrane fuel cells(PEMFCs),as electrochemical devices for the direct combustion-free conversion of chemical to electrical energy,possess many advantages including high efficiency,long life and low environmental pollution,thus have drawn increasing attentions.Proton exchange membrane(PEM)is an important component of’ PEMFCs and its performance directly determines the property of PEMFCs.Nowadays,Dupont’s Nafion has shortcomings,including high cost and proton conductivity loss at high temperature,limiting its wide-scale adoption.Developing some novel PEMs with better performance has become a research hotspot.In recent years,utilizing nanofibers to construct proton-conducting channels has become an important method to improve proton conductivity due to their high specific surface area,large aspect ratio and easy surface modification.Proton transfer is a ubiquitous and significant process in organisms;bacteriorhodopsin has high efficiency of proton pump for optical drive.Many studies have shown that amino acid residues are the material basis for efficient proton transfer.Inspired by this,in this paper,the surface modification of nanofibers is proposed to achieve orderly enrichment of amino acids and construction of efficient proton-conducting channels,and further improve proton conductivity.The main research contents are as follows:Amino acids are immobilized onto the surface of cellulose whiskers with Fmoc-deprotection technology.The SPSF/CW-AAs hybrid PEMs are synthesized by incorporating CW-AAs into sulfonated polysulfone,which are also studied in structures and properties.The experimental results show that the introduction of CW-AAs considerably enhances the thermal stability,water uptake and resistance to methanol of the hybrid PEMs,and effectively improves proton conductivity of hybrid PEMs.The proton conductivity of SPSF/CW-Ser hybrid PEMs can reach 0.234 S/cm at 80 ℃,which is two times higher than that of SPSF.In this work,cellulose nanofibers are further prepared by solution blowing method and modified by amino acids,then SPSF-AAs hybrid PEMs are synthesized by solution vesting.The results exhibit that amino acid clusters on the surface of cellulose nanofibers markedly improve water uptake,proton conductivity and the methanol resistance of hybrid PEMs is also significantly enhanced.The hybrid PEMs of SPSF-Ser exhibit the best proton conductivity of 0.264 S/cm at 80 ℃.Based on the idea that acid-base pairs can significantly improve the efficiency of proton transfer and reduce the energy barrier,acidic PAN-COOH nanofibers are obtained by hydrolysis of PAN nanofibers,then the acid-base pairs reinforced nanofiber hybrid PEMs are prepared by immobilizing basic amino acids(L-Lysine)onto the surface of acidic nano fibers(PAN-COOH).The results show that the introduction of PAN-COOH nanfibers modified by amino acids markedly improves the water absorption and proton conductivity of SPSF/IL-PAN hybrid PEMs.