Investigation of water transport dynamics in polymer electrolyte membrane fuel cells based on high porous micro porous layers Saad S. Alrwashdeh a, b, c, * , Henning Mark € otter a, c , Jan Haußmann d , Tobias Arlt a , Merle Klages d , Joachim Scholta d , John Banhart a, c , Ingo Manke a a Helmholtz-Zentrum Berlin, Hahn-Meitner-Platz 1,14109 Berlin, Germany b Mechanical Engineering Department, Faculty of Engineering, Mu'tah University, P.O Box 7, Al-Karak 61710, Jordan c Technische Universit€ at Berlin, Straße des 17. Juni 135, 10623 Berlin, Germany d Zentrum für Sonnenenergie- und Wasserstoff-Forschung Baden Württemberg (ZSW), Helmholtzstraße 8, 89081 Ulm, Germany article info Article history: Received 13 December 2015 Received in revised form 30 January 2016 Accepted 12 February 2016 Available online xxx Keywords: Polymer electrolyte membrane fuel cell Microporous layer Water transport Radiography Tomography Synchrotron X-ray imaging abstract In this study, synchrotron X-ray imaging is used to investigate the water transport inside newly devel- oped GDM (gas diffusion medium) in polymer electrolyte membrane fuel cells. Two different mea- surement techniques, namely in-situ radiography and quasi-in-situ tomography were combined to reveal the relationship between the structure of the MPL (microporous layer), the operation temperature and the water flow. The newly developed MPL is equipped with randomly arranged holes. It was found that these holes strongly influence the overall water transport in the whole adjacent GDM. The holes act as nuclei for water transport paths through the GDM. In the future, such tailored GDMs could be used to optimize the efficiency and operating conditions of polymer electrolyte membrane fuel cells. © 2016 Elsevier Ltd. All rights reserved. 1. Introduction Fuel cells combined with electric motors are expected to offer alternatives to conventional engines powered by fossil fuels in both mobile and stationary applications [1,2]. For transportation, and here especially in the automotive sector, PEMFC (polymer electro- lyte membrane fuel cells) are considered the most promising fuel cell type. In such PEMFC, a careful water management is crucial to prevent two unfavorable operation situations: Excessive drying of the membrane and flooding of the diffusion media, which was found for example by Wang et al. [1,3e5]. In the first case, the membrane shrinks and loses its proton conductivity, which decreases fuel cell efficiency. In the second case, liquid water in the cell materials blocks gas flow to the catalyst layers. As a consequence, the catalyst layers are undersupplied with gas and the cell performance drops. Hence, a well-balanced water management is an essential condi- tion for optimum power output and long term stability. Optimization of the water transport in the gas diffusion and the microporous layers leads to a better efficiency especially under critical operation conditions that promote flooding. Such condi- tions include temperatures below 60  C as well as high currents that both give rise to elevated water contents [6e9]. There are many possible ways to design the GDM (gas diffusion medium), which consists of the GDL (gas diffusion layer) and, in most cases, a MPL (microporous layer). The morphology and the composition of the fiber substrate (namely the GDL) and the microporous material strongly influence water accumulation and transport [1,10e13]. Different modeling approaches were used to analyze and optimize mass transfer within the porous materials [14e29]. Because neutrons are strongly scattered by hydrogen, imaging methods based on neutrons are very useful to investigated hydrogen distributions within a material [30e35]. For the same reason, neutron imaging is frequently used to investigate the water distribution in operating fuel cells [36e53]. Synchrotron and lab- based X-ray radiography and tomography have been used for investigation of water/media distribution with much higher spatial * Corresponding author. Helmholtz-Zentrum Berlin, Hahn-Meitner-Platz 1,14109 Berlin, Germany. Tel.: þ49 30 8062 42825; fax: þ49 30 8062 43059. E-mail address: saad.alrwashdeh@helmholtz-berlin.de (S.S. Alrwashdeh). Contents lists available at ScienceDirect Energy journal homepage: www.elsevier.com/locate/energy http://dx.doi.org/10.1016/j.energy.2016.02.075 0360-5442/© 2016 Elsevier Ltd. All rights reserved. Energy 102 (2016) 161e165