The surface coverage of PEM fuel cell electrodes F. Dundar a,b,* , A. Pilenga b , G. Tsotridis b a Department of Mechanical Engineering, Meliksah University, 38280, Kayseri, Turkey b Institute for Energy and Transport, Joint Research Centre, European Commission, Postbus 2, 1755 ZG Petten, The Netherlands article info Article history: Received 4 June 2015 Received in revised form 8 September 2015 Accepted 22 October 2015 Available online 12 November 2015 Keywords: Fuel cells Carbon monoxide Coverage Desorption Impurity Bond strength abstract A quantitative study was conducted on Hydrogen (H 2 ), water (H 2 O) and carbon monoxide (CO) molecule concentration on a PteRu catalyst surface used for PEM fuel cells. Strongly bonded hydrogen molecules which can withstand 100 ppm CO exposure at 50  C were calculated as 54% of the total hydrogen bonds present on catalyst surface during pure H 2 purge. The very weakly bonded hydrogen molecules that could be removed with pure inert gasses were not taken into account. Additionally, the water and hydrogen molecule con- tent on the surface of the catalyst layer was compared and bonded hydrogen molecule ratios of 33e63% were obtained for different temperatures (25  C, 50  C and 75  C) and relative humidity values (Dew Point Temperatures of 25  C, 35  C and 45  C). Furthermore, 10 ppm CO exposure time at dry conditions was varied from 30 s to 1 h at 50  C. The majority of the weakly adsorbed hydrogen molecules desorbed in the first 10 min with 300 sccm gas flow over PteRu catalyst layer. The desorption process stopped after 10 min. The hydrogen molecules were bonded strong enough to stick to the surface under 10 ppm CO exposure at 50  C. The bonded hydrogen molecule ratio of 66e67% was calculated for 10 e60 min of 10 ppm CO exposure. Copyright © 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved. Introduction Polymer Electrolyte Membrane (PEM) fuel cells are promising energy converters for the coming decade. The high energy density and continuous power generation capability puts them ahead of other energy deposition technologies as the primary electricity supplier for portable and stationary appli- cations. However, their positive features are yet to be devel- oped to commercialize particularly for automotive industry. High cost, infrastructure and durability problems are among the severe barriers to overcome [1]. A huge improvement was accomplished during the last decade on PEM fuel cells. The cost of a typical 80 kW auto- motive PEM fuel cell system declined from 275 $/kW to 47 $/ kW within 10 years (2002e2012) [2]. This was accomplished by intensive research efforts. Catalyst research is the highest funded research category for fuel cells according to United States (US) Department of Energy (DOE) [2] followed by sys- tems and balance of plant, durability, analysis and testing, mass transport, MEA integration, impurities and membrane studies. The increasing interest on catalyst, durability and impurity studies shows the importance of durability on cata- lyst surfaces as a major cost item. * Corresponding author. Department of Mechanical Engineering, Meliksah University, 38280, Kayseri, Turkey. Tel.: þ90 533 578 9251. E-mail address: fdundar@meliksah.edu.tr (F. Dundar). Available online at www.sciencedirect.com ScienceDirect journal homepage: www.elsevier.com/locate/he international journal of hydrogen energy 41 (2016) 497 e504 http://dx.doi.org/10.1016/j.ijhydene.2015.10.088 0360-3199/Copyright © 2015, Hydrogen Energy Publications, LLC. Published by Elsevier Ltd. All rights reserved.