Journal of Power Sources 187 (2009) 363–370 Contents lists available at ScienceDirect Journal of Power Sources journal homepage: www.elsevier.com/locate/jpowsour Preparation of Pt–Ru catalysts on Nafion(Na + )-bonded carbon layer using galvanostatic pulse electrodeposition for proton-exchange membrane fuel cell Youngmi Ra a , Jaeseung Lee b , In Kim a , Sungyool Bong a , Hasuck Kim a,∗ a Department of Chemistry, Seoul National University, San 56-1, Sillim 9-dong, Kwanak-gu, Seoul 151-747, Republic of Korea b Hyundai Motor Company, 104 Mabuk-dong, Giheung-gu, Yongin-si, Gyeonggi-do 446-912, Republic of Korea article info Article history: Received 30 May 2008 Received in revised form 15 August 2008 Accepted 26 October 2008 Available online 21 November 2008 Keywords: Proton-exchange membrane fuel cell Electrodeposition Platinum–ruthenium alloy Catalyst utilization efficiency Carbon dioxide tolerance abstract Platinum–ruthenium (Pt–Ru) on a Nafion(Na + )-bonded carbon layer is fabricated by using galvanos- tatic pulse electrodeposition for high utilization of catalysts and cost reduction. The composition of the Pt–Ru electrode, which is controlled by varying the concentration of the Ru precursor, is deter- mined by inductively coupled plasma-atomic emission spectroscopy and by electron probe microanalysis. The particle size of the electrodeposited Pt–Ru catalyst is determined by high-resolution transmission electron microscopy. Other characterizations are carried out by X-ray diffraction, X-ray photoelectron spectroscopy, and CO-stripping voltammetry. Electrodeposited Pt–Ru catalysts give improved perfor- mance, not only in single-cell operations but also with respect to CO tolerance compared with electrodes prepared by conventional means. The behaviour is probably due to enhanced utilization of the catalysts. Recovery from CO exposure demonstrates that the electrodeposited catalysts exhibit better resistance to CO. © 2008 Elsevier B.V. All rights reserved. 1. Introduction Among the various fuel cells, proton-exchange membrane fuel cells (PEMFCs) as energy conversion devices are promising future power systems with high power density, energy efficiency, and low operating temperature [1–4]. Nevertheless, a PEMFC operat- ing with hydrogen (H 2 ) gas containing carbon monoxide (CO) from the reforming of fossil fuels shows low performance. This problem is caused by CO poisoning of the catalyst. The gas blocks the Pt sur- face because the bond strength of Pt–CO is greater than that of Pt–H, and thereby decreases the activity of the anode [5–8]. In order to improve the CO tolerance of the anode, many studies in recent years have reported details of new preparation meth- ods and different compositions of Pt-based catalysts such as Pt–Ru, Pt–Sn and Pt–Mo [5,6,8–12]. In particular, the Pt–Ru system is an excellent anode electrocatalyst since it exhibits enhanced CO tol- erance, which can be attributed to a bifunctional mechanism as follows [12]: Ru + H 2 O → Ru–OH ads + H + + e - (1) Pt–CO ads + Ru–OH ads → CO 2 + Pt + Ru + H + (2) Pt–Ru electrodes for PEMFCs [13] have been prepared by var- ious methods such as the colloidal [14,15], impregnation [16] and ∗ Corresponding author. Tel.: +82 2 880 6638; fax: +82 2 880 6638. E-mail address: hasuckim@snu.ac.kr (H. Kim). electrodeposition [5,17–19] methods. Catalyst powders synthesized by means of the colloidal and impregnation methods were well- mixed with ionic binder (e.g., Nafion solution) and then spread on a gas diffusion layer (GDL). After this procedure, the mem- brane electrode assembly (MEA) was generally fabricated using the prepared electrode and a Nafion membrane. This method does, however, produce a large number of inactive catalyst sites because the catalytic reaction occurs only at the interface between the membrane and the electrode that is exposure to the reactant, known as the triple-phase boundary (Fig. 1(a)) [17]. Also, ionic binder is added to the electrode in order to extend the triple-phase boundaries. As the result, it increases the production cost of the electrode [20]. The electrodeposition method – a way to overcome the cost problem – makes catalysts that are deposited directly on the surface of the substrate. Therefore, it offers not only enhanced catalyst uti- lization (Fig. 1(b)) but also simplification of preparation. In general, electrodeposition can be carried out by using either a potentio- static [23–25] or galvanostatic method, which involves direct and pulse techniques. Electrodeposition via the galvanostatic pulse technique is considered convenient to improve the current distribu- tion, therefore, it is easy to control the particle size and composition of the alloy simply by varying experimental parameters such as on/off time and peak current density [20–22]. Coutanceau et al. [18] and Wei and Chan [19] reported the preparation of an Pt–Ru anode for direct methanol fuel cells by using a galvanostatic pulse technique. They obtained catalysts with a 1:1 atomic ratio and improved performance. Alcaide et al. [5] obtained enhanced CO 0378-7753/$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.jpowsour.2008.10.135