Journal of Power Sources 183 (2008) 62–68 Contents lists available at ScienceDirect Journal of Power Sources journal homepage: www.elsevier.com/locate/jpowsour Effect of preparative parameters on the characteristic of poly(vinylidene fluoride)-based microporous layer for proton exchange membrane fuel cells Ai Lien Ong, Aldo Bottino ∗ , Gustavo Capannelli, Antonio Comite Dipartimento di Chimica e Chimica Industriale, via Dodecaneso 31, 16146 Genova, Italy article info Article history: Received 19 February 2008 Received in revised form 14 April 2008 Accepted 27 April 2008 Available online 4 May 2008 Keywords: PVDF Microporous layer Gas diffusion layer Electrically conductive filler PEM fuel cell abstract The effect of preparative parameters on the characteristic of PVDF-based microporous layers (MPL) for pro- ton exchange membrane (PEM) fuel cell was investigated. Physical properties of MPL involving electrical resistance, gas permeability and microstructure were examined. The results show that the characteristics of MPL were affected by preparative parameters, such as PVDF concentration, type of electrically conduc- tive filler and its loading, PVDF/electrically conductive filler ratio, as well as type of PVDF solvent. The PEM fuel cell performance test demonstrates that the obtained MPL has a great potential and interest for further study and development. © 2008 Published by Elsevier B.V. 1. Introduction In responding to the challenge of satisfying the rapid increase in the global demand of energy while developing environment friendly forms of power generation to reduce air pollution and lessen the threat of global warming, proton exchange membrane fuel cells (PEMFC) are becoming one of the potential alternative power sources. However, the prohibitive cost of the PEMFC in con- junction with the problem of low reliability and durability presently are the major obstacles to its commercialization [1–3]. The per- formance and cost of a PEMFC are critically dependent on the electrocataytic activity of the noble metal platinum (Pt) catalyst [4–6], as well as on material selection, fabrication processes and performance of its various components, such as proton exchange membrane (PEM) [7–9], gas diffusion layers (GDL) [10–12] and bipolar plates [13–15]. PEM also called as catalyst-coated membrane if the electrocat- alyst is formerly attached to the PEM, requires a certain amount of water for high proton conduction; however, the exceeding water can be easily condensed to liquid water phase within the gas dif- fusion electrodes, in which this phenomena is defined as water flooding [16,17]. This liquid water phase may drastically decrease the PEMFC performance by hindering gas diffusion, as well as by covering the active sites of the electrocatalysts, forming a dead ∗ Corresponding author. Tel.: +39 0103538724; fax: +39 0103538759. E-mail address: bottino@chimica.unige.it (A. Bottino). reaction zone [16–19]. Therefore, the porous GDL is one of the key components in PEMFC, as it promotes effective transportation of gas reactants to the catalyst layers, providing low electronic resistance (due to its surface that enhances good electronic contact between bipolar plate and catalyst), allowing an optimal catalyst utilization. Finally, it ensures an efficient water management allowing water- flooding prevention because of its proper hydrophobicity. A GDL consists of a gas diffusion-backing layer, also called macroporous substrate, made of either a woven carbon cloth or a non-woven carbon paper (due to their good electrical conductivity, poros- ity and mechanical strength) with or without microporous layer (MPL). The MPL is an electrically conductive layer, commonly com- posed by carbon black powder and hydrophobic agent. It can be applied on one side or both sides of the gas diffusion-backing layer. The role of MPL is to enhance further the performance of a GDL by minimizing electronic contact resistance, improving gas trans- port and reducing the water-flooding tendency thanks to a proper structure, pore size and distribution and also its hydrophobic char- acter. The improved performance of a GDL, due to the presence of MPL, is a recent subject of extensive attention. Aityeh et al. [20] reported that PEMFC with a carbon–polytetrafluoroethylene (PTFE) MPL on either electrode or on both electrodes provided a better overall performance and durability compared to cells with- out a MPL. Zhan et al. [21] analyzed the distribution of liquid water phase saturation for different GDL structures and concluded that gas diffusion increased with the increase of porosity as well as the porosity gradient along the MPL thickness. Tang et al. [22] 0378-7753/$ – see front matter © 2008 Published by Elsevier B.V. doi:10.1016/j.jpowsour.2008.04.064