Synthesis of highly stable and high water retentive functionalized biopolymer-graphene oxide modified cation exchange membranes

Abstract

Utility of Polymer electrolyte membrane in energy based devices is substituting the conventional electrolyte. Herein, we have synthesized PEM based biopolymer, functionalized silica modified GO and PVA. GO is modified in two steps to synthesize silica grafted sulfonated GO.Functionalization of chitosan is done using 1,3 propane sultone after deacetylation. Further, PVA has been used as a polymer matrix since PVA possess good film forming property with mechanical stability. Different weight % (1, 2 and 5) of modified GO has been incorporated in the chitosan matrix. Prepared PEMs are subjected to different characterization such as structural, thermal, mechanical and electrochemical etc. The nano-hybrid membranes shows the significant increment in electrochemical properties. MGO-SCH-5 membrane shows the proton conductivity as 6.77 ×10 −2 S cm -1 which goes to increases upto 11.2×10 −2 S cm -1 at 90 0 C. Thermal and mechanical stability of PEM also gets increases with the MGO content in to sulfonated chitosan.The elastic modulus for MGO-SCH-5 membrane is calculated to 21.37 MPa with 54 MPa of maximum stress. Thus membranes may be targeted as PEM for higher temperature energy application. IntroductionPolymer electrolyte membranes (PEM) are playing a vital role in energy based devices, and replacing liquid electrolyte in fuel cells and batteries due to their ease of handling and excellent physico-chemical as well as mechanical properties etc. [1][2][3][4]. Composite membranes are the subject of intense research as well as are ideal work of art due to its excellent properties [5][6]. To date, various kind of fillers have been incorporated into polymer matrix to enhance the membrane performance for different applications [7][8][9][10]. Different type carbon based materials such as carbon quantum dots, graphene oxide, C 60 and carbon nanotube have been incorporated within the polymeric membranes and they have displayed significant enhancement in the membrane performance. Different types of oxides and conducting polymers have also been incorporated into the PEM to enhance its applicability and stability [11][12]. An ideal PEM must have high ionic conductivity, high thermal, mechanical stability and high methanol crossover resistance to be employed as solid electrolyte for fuel cell application. Fascinating properties of Graphene oxide (GO) makes it a material of interest and in past few years research on GO is rising and it can be estimated by the increasing number of publications [6]. Applicability of GO has been realized for many applications and many other are yet to be explored [13]. Use of GO in polymer electrolyte membrane has been done in our previous work [7]. Further, GO has also been modified with different metals, metal oxides etc. by many researchers [8]. Modification of GO with silica is an effective strategy to increase the stability of material, since silica is a low cost and abundant material. GO-silica composite has been prepared by Zhang et. Al. for electroreponsive characteristics [9]. High ionic conduct...

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“…Generally, graphite is the source used to prepare GO . GOs can exfoliate into individual graphite oxide nanoplatelets in water, forming a homogeneous solution, due to the presence of these hydrophilic oxygen groups .…”

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