Journal of Power Sources 196 (2011) 7426–7434 Contents lists available at ScienceDirect Journal of Power Sources jou rnal h omepa g e: www.elsevier.com/locate/jpowsour Tungsten carbide modified high surface area carbon as fuel cell catalyst support Minhua Shao a,∗ , Belabbes Merzougui a,1 , Krista Shoemaker a , Laura Stolar a , Lesia Protsailo a , Zachary J. Mellinger b , Irene J. Hsu b , Jingguang G. Chen b,∗ a UTC Power, 195 Governor’s Highway, South Windsor, CT 06074, USA b Department of Chemical Engineering, University of Delaware, Newark, DE 19716, USA a r t i c l e i n f o Article history: Received 7 March 2011 Received in revised form 7 April 2011 Accepted 8 April 2011 Available online 20 April 2011 Keywords: Fuel cell catalysts Oxygen reduction reaction Corrosion X-ray absorption near edge structure Activity Durability a b s t r a c t Phase pure WC nanoparticles were synthesized on high surface area carbon black (800 m 2 g -1 ) by a temperature programmed reaction (TPR) method. The particle size of WC can be controlled under 30 nm with a relatively high coverage on the carbon surface. The electrochemical testing results demonstrated that the corrosion resistance of carbon black was improved by 2-fold with a surface modification by phase pure WC particles. However, the WC itself showed some dissolution under potential cycling. Based on the X-ray diffraction (XRD) and inductively coupled plasma (ICP) analysis, most of the WC on the surface was lost or transformed to oxides after 5000 potential cycles in the potential range of 0.65–1.2 V. The Pt catalyst supported on WC/C showed a slightly better ORR activity than that of Pt/C, with the Pt activity loss rate for Pt/WC/C being slightly slower compared to that of Pt/C. The performance and decay rate of Pt/WC/C were also evaluated in a fuel cell. © 2011 Elsevier B.V. All rights reserved. 1. Introduction One of the main factors limiting the lifetime of proton exchange membrane fuel cells (PEMFCs) is the degradation of the electrocat- alyst layer, in particular, corrosion of the carbon support [1–5]. The corrosion rate of carbon black at potentials lower than 0.9 V is rea- sonably slow at the typical operating temperatures (60–90 ◦ C) of the PEMFCs. However, long-term operations can cause a decrease in carbon content in the catalyst layers [3]. In particular, during extended operation with start–stop cycling and fuel starvation, the cathode can experience high potentials up to 1.5 V [6,7]. Under these conditions, severe carbon corrosion occurs, causing catalyst particle agglomeration, and increasing the ohmic resistance and the gas diffusion resistance due to collapse of the porous structure. More stable support materials are strongly needed to improve the stability and durability of the catalyst layers [3]. Metal carbides, especially tungsten monocarbide (WC), have been proposed as catalyst support for fuel cells due to their high stability, low electrical resistivity, and strong interaction with the metal catalysts [8–16]. Chhina et al. [12] compared the stability of Pt supported on tungsten carbide to that supported on Vulcan ∗ Corresponding authors. Tel.: +1 860 727 7251; fax: +1 860 660 7384. E-mail addresses: Minhua.shao@utcpower.com (M. Shao), jgchen@udel.edu (J.G. Chen). 1 Current address: Center of Excellence in Nanotechnology (CENT) & Department of Chemistry, KFUPM, Dhahran 31261, Saudi Arabia. XC-72 and found that the former could retain the surface area and activity better during the corrosion testing in acid. The high stabil- ity of tungsten carbides in the electrochemical testing was assigned to a core–shell type structure that was formed when the surface of tungsten carbides were oxidized to WOx, forming a passive shell encapsulating the carbide core. It is important, however, to note that the stability of tungsten carbides also depends on the struc- ture, phase, and shape. For instance, it has been reported that WC is more stable than W 2 C in the acidic medium [10,17]. In addition to the high stability, tungsten carbides are also expected to enhance the catalytic activity of the Pt nanoparticle due to the strong metal–support interaction (SMSI) [18]. Shen’s group reported that the oxygen reduction reaction (ORR) activi- ties of Pt and Pd based catalysts were enhanced significantly on the tungsten carbides modified carbon supports [19–22]. The pos- sible reasons for the observed activity enhancement include more uniform catalyst distribution on the modified carbon and the syn- ergistic interaction between metal particles and tungsten carbides. Such interaction may cause some change in electronic environment of Pt leading to low oxide formation on the surface of Pt, which is believed to be one of the causes for Pt dissolution [1]. The synthesis of high surface area WC as the support for Pt cat- alyst is a great challenge. One alternative way to take advantage of the high stability and SMSI of WC is to coat the high surface area carbon black with a relatively uniform nano-structured WC coating (film or small nanoparticles). Several previous studies reported the modification of carbon support with large carbides powder mixed with WC and W 2 C phases [8,12,23]. In the present work, we focus 0378-7753/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.jpowsour.2011.04.026