Facile Preparation of Well-Dispersed GO-SPEEK Composite Membranes by Electrospun for Fuel Cell Applications
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Facile Preparation of Well-Dispersed GO-SPEEK Composite Membranes by Electrospun for Fuel Cell Applications Xu Liu, Xiaoyu Meng, Chuanming Shi, Jiangbei Huo, Ziqing Cai, Lishan Cui, Qiong Zhou Department of Materials Science and Engineering, China University of Petroleum-Beijing, Beijing 102249, China ABSTRACT Graphene oxide (GO) is one of the most attractive inorganic nanofillers in proton exchange membranes (PEMs) for its large specific surface area and high proton conductivity. The proton conductivity of GO nanosheet is known to be orders of magnitude greater than the bulk GO, thus it is essential to improve the dispersion of GO nanosheets in the PEM matrix to achieve higher conductivity. In this study, we report a facile and effective method to fabricate a GO/sulfonated poly ether ether ketone (SPEEK) composite membrane with well-dispersed GO nanosheets in SPEEK matrix by using electrospinning technique for direct methanol fuel cell application. The composite membrane exhibits improved proton conductivity, dimensional stability and methanol barrier property due to the presence of well-dispersed GOs. It is believed that the GO nanosheets can not only induce continuous channels for proton-conducting via Grotthuss mechanism, but also act as methanol barriers to hinder the methanol molecules from passing through the membrane. INTRODUCTION PEM is a key component in direct methanol fuel cells (DMFCs), acting as an electrolyte for transferring protons and a barrier for methanol permeation [1]. The most widely used commercial Nafion® membrane has high proton conductivity but also high methanol permeability and high cost [2]. SPEEK, the most promising candidate as an alternative to Nafion®, has been intensively studied for its low cost, good mechanical property and excellent thermal and chemical stability [3]. The proton conductivity, methanol permeability, water uptake and dimension stability of SPEEK membranes are all depended on the degree of sulfonation (DS) of SPEEK. Low DS leads to inferior conductivity but good dimension stability, low methanol permeability and water uptake. On the contrary, high DS SPEEK exhibits high proton conductivity but high methanol permeability and water uptake, poor dimensional stability. In order to achieve a good balance of these properties, many research groups have focused on the incorporation of inorganic fillers [4]. GO is particularly attractive as inorganic nanofiller in PEMs. Numerous of -O-, -OH and –COOH groups at both sides and edges of GO nanosheet can attract the protons, forming hydrogen bond networks for proton transport. It has been demonstrated that the proton
conductivity of GO nanosheet is several orders of magnitude greater than bulk GO [5]. In order to achieve a homogeneous dispersion of GO in polymer matrix, many efforts have been made on the chemical modification of GO. As is well-known, electrospinning is a simple and effective method for the fabrication of inorganic-organic hybrid nanofibers [6]. During electrospun process nanofillers can be finely dispersed in
