Electrochimica Acta 56 (2011) 9370–9377 Contents lists available at ScienceDirect Electrochimica Acta j ourna l ho me pag e: www.elsevier.com/locate/electacta Electrochemical stability of carbon nanofibers in proton exchange membrane fuel cells Garbi ˜ ne Álvarez a , Francisco Alcaide a,∗,1 , Oscar Miguel a , Pere L. Cabot b,1 , M.V. Martínez-Huerta c , J.L.G. Fierro c a Energy Department, CIDETEC-IK4, P ◦ Miramón, 196, 20009 San Sebastián, Spain b Laboratori d’Electroquímica de Materials i del Medi Ambient, Dept. Química Física, Universitat de Barcelona, Martí i Franquès, 1-11, 08028 Barcelona, Spain c Instituto de Catálisis y Petroleoquímica (CSIC), Marie Curie 2, Cantoblanco, 28049 Madrid, Spain a r t i c l e i n f o Article history: Received 21 June 2011 Received in revised form 4 August 2011 Accepted 5 August 2011 Available online 17 August 2011 Keywords: Catalyst support Carbon nanofibers Carbon corrosion Durability PEMFC a b s t r a c t This fundamental study deals with the electrochemical stability of several non-conventional carbon based catalyst supports, intended for low temperature proton exchange membrane fuel cell (PEMFC) cathodes. Electrochemical surface oxidation of raw and functionalized carbon nanofibers, and carbon black for comparison, was studied following a potential step treatment at 25.0 ◦ C in acid electrolyte, which mim- ics the operating conditions of low temperature PEMFCs. Surface oxidation was characterized using cyclic voltammetry, X-ray photoelectron spectroscopy (XPS), and contact angle measurements. Cyclic voltam- mograms clearly showed the presence of the hydroquinone/quinone couple. Furthermore, identification of carbonyl, ether, hydroxyl and carboxyl surface functional groups were made by deconvolution of the XPS spectra. The relative increase in surface oxides on carbon nanofibers during the electrochemical oxi- dation treatment is significantly smaller than that on carbon black. This suggests that carbon nanofibers are more resistant to the electrochemical corrosion than carbon black under the experimental conditions used in this work. This behaviour could be attributed to the differences found in the microstructure of both kinds of carbons. According to these results, carbon nanofibers possess a high potential as catalyst support to increase the durability of catalysts used in low temperature PEMFC applications. © 2011 Elsevier Ltd. All rights reserved. 1. Introduction Proton exchange membrane fuel cells (PEMFCs) are being used as power sources for automotive, stationary and portable appli- cations [1], because they have a high flexibility, low temperature range, ability for fast load changes and fast start-up. Furthermore, they have high efficiency, high current density output and low emissions. Until not long time ago, fuel cell research activities in PEMFC technology were directed towards increasing power density and efficiency. Nowadays, the focus of PEMFC research and devel- opment is shifting to durability and cost issues, the other requirements which will guarantee a successful commercializa- tion of PEMFC systems [2,3]. In this context, platinum supported on carbon, the catalyst of choice used in PEMFC electrodes, is play- ing a key role because it is one of the most expensive components in PEM cells and stacks [4]. As a consequence, it is necessary to reduce the amount of precious metal used in electrodes to get a ∗ Corresponding author. Tel.: +34 943 309 022; fax: +34 943 309 136. E-mail address: falcaide@cidetec.es (F. Alcaide). 1 ISE members. good performance/cost ratio. This can also be achieved by combin- ing platinum with other metals to form alloys, a good synthesis procedure of the catalyst which allows the homogeneous deposi- tion of finely divided Pt-containing particles on high surface area carbon supports, or a proper electrode configuration. Catalyst dura- bility is another issue which should be improved. For example, for automotive and stationary applications a durability of 5000 and 40,000 h is required, respectively [5–7]. To accomplish these durability requirements the catalyst should have a high resistance against corrosion in the fuel cell environment [8]. One solution could be the use of new carbon materials as catalyst supports. Carbonaceous materials used as support for platinum nanopar- ticles and alloys are receiving increasing attention, because their degradation affects negatively the performance and durability of PEMFCs [9,10]. In fact, the extreme operating conditions found in a PEMFC, which include high humidity, low pH (<1), and strongly oxidizing (O 2 ) or reducing (H 2 ) atmosphere at the cathode or at the anode, respectively, contribute to accelerate carbon corrosion [11,12]. Even more, corrosion can also occur during the fuel cell power change under normal operation, and in particular during start-up/shut-down steps, where the potential of carbon attains very high values (1.2–1.5 V) [13,14] and also under the conditions of the “reverse current” phenomena [15,16]. In addition to the 0013-4686/$ – see front matter © 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.electacta.2011.08.022