Electrochimica Acta 54 (2009) 6515–6521 Contents lists available at ScienceDirect Electrochimica Acta journal homepage: www.elsevier.com/locate/electacta Corrosion resistance and sintering effect of carbon supports in polymer electrolyte membrane fuel cells Hyung-Suk Oh, Katie Heeyum Lim, Bumwook Roh 1 , Inchul Hwang 1 , Hansung Kim ∗ Department of Chemical and Biomolecular Engineering, Yonsei University, 134 Shinchon-Dong, Seodaemun-gu, 120-749, Seoul, South Korea article info Article history: Received 13 March 2009 Received in revised form 9 June 2009 Accepted 12 June 2009 Available online 21 June 2009 Keywords: Carbon nanocage Carbon corrosion Mass spectrometry PEM fuel cell abstract The corrosion resistance of carbon black, carbon nanofiber and carbon nanocage used as catalyst sup- ports in fuel cells was investigated by monitoring CO 2 emission using on-line mass spectrometry when 1.4 V was applied for 30 min. The changes associated with the carbon corrosion were assessed through electrochemical methods. In general, graphitized carbon supports were more corrosion-resistant than amorphous carbon black. However, the degree of graphitization did not directly correlate with higher resistance to corrosion. Hydrophobicity was critical in enhancing resistance to corrosion. When sinter- ing of Pt particles was considered, carbon nanocages were more resistant than nanofibers. The present findings thus indicate that the carbon nanocage is an appropriate catalyst support in fuel cell systems. © 2009 Elsevier Ltd. All rights reserved. 1. Introduction Carbon black (CB) supports with high surface areas have been widely used in polymer electrolyte membrane fuel cells (PEMFCs). However, electrochemical carbon corrosion is a major contribu- tor to performance degradation during fuel cell operation [1–3]. Carbon corrosion diminishes fuel cell performance by causing aggregation and loss of the Pt catalyst. Generally, the thermody- namic potential for carbon corrosion under standard conditions is only 0.207V vs. NHE, which means that electrochemical oxi- dation of carbon is thermodynamically favorable only above this voltage. However, because the electrochemical kinetic of carbon corrosion is slow, severe carbon corrosion is not observed under normal PEMFC operating conditions [4]. However, the rate of cor- rosion accelerates during abnormal operating conditions such as fuel starvation and repetitive start-up/shut-down processes, which induce cathode potentials in excess of 1.4V [5–7]. Such potentials easily oxidize carbon supports, resulting in a rapid degradation of fuel cell performance. Several recent studies have sought to alleviate the problems associated with carbon corrosion. These works can be classified into three categories which are graphitized carbon [8–10], metal oxides [11–13], and conductive polymers [14–16]. Most attention has focused on the use of graphitized carbon as a catalyst support. Shao and colleagues showed that a catalyst supported on multi- ∗ Corresponding author. Tel.: +82 2 2123 5753; fax: +82 2 312 6401. E-mail address: elchem@yonsei.ac.kr (H. Kim). 1 Hyundai Motor Company, Mabuk-Ri, Gyeonggi-Do, Korea. walled carbon nanotubes was more corrosion-resistant than when supported on carbon black of vulcan XC-72 [17]. Ye and co-workers reported that the corrosion resistance of a carbon support was related to intrinsic graphitic character. The more graphitic the struc- ture, the more resistant was the carbon to corrosion [18]. However, the relationship between degree of graphitization and corrosion resistance of a carbon support remains unclear. In the present study, we addressed this problem by conduct- ing corrosion tests on different carbon supports including carbon black, carbon nanofiber (CNF), and carbon nanocage (CNC) which exhibit different degrees of graphitization and varied morphology. We monitored CO 2 emission using on-line mass spectrometry to obtain direct evidence of electrochemical carbon corrosion [19]. 2. Experimental Three different carbon supports were investigated. Ketjen Black 300J is an amorphous carbon black, whereas CNF of the platelet-type and CNC are graphitized carbons. Carbon-supported Pt catalysts with 40 wt% Pt were synthesized using the modified polyol process described in our previous work [20]. The graphical presentation of three different types of carbon supported Pt parti- cles is shown in Fig. 1. A commercial Pt/C catalyst (40 wt% Pt) from Johnson Matthey Co. was used as the anodic catalyst. Synthesized catalysts were ultrasonically mixed with 5wt% Nafion ionomer in isopropanol. Next, membrane electrode assemblies (MEAs) were created by spray-depositing the mixed slurry onto a Nafion 212 membrane. The cell area was 5 cm 2 and the amount of Pt loaded was 0.4 mg cm -2 . Each MEA was loaded into a fully automated single-cell test station, and the cell was allowed to stabilize until 0013-4686/$ – see front matter © 2009 Elsevier Ltd. All rights reserved. doi:10.1016/j.electacta.2009.06.028