Hydroxide-ion selective electrolytes based on a polybenzimidazole/ graphene oxide composite membrane Bor-Chern Yu a , Yi-Chun Wang a , Hsin-Chun Lu a , Hsiu-Li Lin b , Chao-Ming Shih a , S. Rajesh Kumar a , Shingjiang Jessie Lue a, c, d, * a Department of Chemical and Materials Engineering and GreenTechnology Research Center, Chang Gung University, Guishan District, Taoyuan City 333, Taiwan b Department of Chemical Engineering and Materials Science and Fuel Cell Center, Yuan Ze University, Chung-Li, Taoyuan City 320, Taiwan c Department of Radiation Oncology, Chang Gung Memorial Hospital, Guishan District, Taoyuan City 333, Taiwan d Department of Safety, Health and Environmental Engineering, Ming-Chi University of Technology, Taishan District, New Taipei City 243, Taiwan article info Article history: Received 28 January 2017 Received in revised form 1 June 2017 Accepted 9 June 2017 Available online 12 June 2017 Keywords: Graphene oxide (GO) Polybenzimidazole (PBI) Spin coating Alkaline fuel cell Cell performance abstract The objectives of this work are to prepare and characterize poly[2,2 0 -m-(phenylene)-5,5 0 -bibenzimida- zole]/graphene oxide (PBI/GO) solid electrolyte for direct alcohol alkaline fuel cell (DAAFC) applications. GO nanosheets are coated onto a PBI surface using a spin coater to construct the PBI/GO composite membrane. The PBI/GO composite membrane exhibits an ionic conductivity of 2.53  10 2 S cm 1 at 80  C, which is improved by 72e93% when compared with the pure PBI membrane. In addition, the methanol permeability is reduced by 18e25% by incorporating GO onto the PBI top surface. The peak power density (P max ) of the PBI/GO electrolyte reaches 200 mW cm 2 when using alkaline methanol as fuel with Pt-based catalysts, or 120 mW cm 2 when fed with an ethanol and alkaline solution mixture at 80  C. Replacing the Pt-based catalysts with Hypermec™ catalysts resulted in P max of 40 and 100 mW cm 2 , for methanol and ethanol fuel cells, respectively. These superior DAAFC power outputs are ascribed to the improved anion conduction of the KOH doped GO and the suppressed methanol cross-over from high aspect ratio GO as the alcohol barrier layer. © 2017 Elsevier Ltd. All rights reserved. 1. Introduction Fuel cells are electro-chemical conversion devices able to transform chemical energy into electrical energy and thereby function as alternative power resources [1,2]. Recently, low- operating temperature (<80  C) fuel cells, including acidic direct alcohol fuel cells (DAFCs) [3] and alkaline DAFCs have been pro- posed for mobile and portable applications [4,5]. As a key compo- nent of acidic DAFCs, Nafion from DuPont has been used as a cationic-exchange membrane (CEM) due to its high chemical resistance and outstanding physical strength [6,7]. CEMs can transport protons from anode to cathode and act as a barrier to separate the fuel and oxidant streams [8,9]. The bottlenecks for acidic DAFCs in commercialization are slow redox kinetics, platinum-based electrocatalysts, high fuel permeability, CO poisoning, complex water management and their high cost [10e12]. In contrast, alkaline DAFCs employing an anion-exchange membrane (AEM) are a potential alternative to DAFCs employing a CEM and have attractive merits [13,14]. The advantages of alkaline DAFCs include suppressed fuel cross-over, enhanced electro- chemical kinetics, easy water management and reduced cost [15e18]. Methanol, being rich in hydrogen, has become a popular fuel in addition to hydrogen. Consequently the use of direct methanol alkaline fuel cells (DMAFCs) in alternative energy applications has gained significant attention [19e21]. During DMAFC operation, the hydroxide anion acts as a charge carrier and transfers from cathode to anode, which is contrary to the proton migration direction in acidic direct methanol fuel cells (DMFC) [22]. Thus, the electro- osmotic effect of anions accompanies reduced methanol cross- over through the electrolyte film. The electrochemical reactions of methanol oxidation [23] and oxygen reduction [24] are easily accelerated in an alkaline solution than those of acidic medium. Water molecules are generated at the anode and compatible with * Corresponding author. Department of Chemical and Materials Engineering, Chang Gung University, Guishan District, Taoyuan City 333, Taiwan. E-mail address: jessie@mail.cgu.edu.tw (S.J. Lue). Contents lists available at ScienceDirect Energy journal homepage: www.elsevier.com/locate/energy http://dx.doi.org/10.1016/j.energy.2017.06.061 0360-5442/© 2017 Elsevier Ltd. All rights reserved. Energy 134 (2017) 802e812