Electrochimica Acta 75 (2012) 191–200 Contents lists available at SciVerse ScienceDirect Electrochimica Acta journal homepage: www.elsevier.com/locate/electacta Co-deposition of Pt and ceria anode catalyst in supercritical carbon dioxide for direct methanol fuel cell applications Eunyoung You a , Rolando Guzmán-Blas b , Eduardo Nicolau b , M. Aulice Scibioh b , Christos F. Karanikas a , James J. Watkins c,∗ , Carlos R. Cabrera b,∗ a Department of Chemical Engineering, University of Massachusetts, Amherst, MA 01003, USA b Department of Chemistry and NASA Center for Advanced Nanoscale Materials, University of Puerto Rico, Rio Piedras Campus, PO Box 70377, San Juan, PR 00936-8377, USA c Department of Polymer Science and Engineering, University of Massachusetts, Amherst, MA 01003, USA article info Article history: Received 29 December 2011 Received in revised form 28 February 2012 Accepted 25 April 2012 Available online 3 May 2012 Keywords: Supercritical fluid deposition Methanol oxidation Platinum-ceria Carbon dioxide Thin-layer electrode Direct methanol fuel cell abstract Pt and mixed Pt-ceria catalysts were deposited onto gas diffusion layers using supercritical fluid deposi- tion (SFD) to fabricate thin layer electrodes for direct methanol fuel cells. Dimethyl (1,5-cyclooctadiene) platinum (II) (CODPtMe 2 ) and tetrakis (2,2,6,6-tetramethyl 3,5-heptanedionato) cerium (IV) (Ce(tmhd) 4 ) were used as precursors. Hydrogen-assisted Pt deposition was performed in compressed carbon dioxide at 60 ◦ C and 17.2 MPa to yield high purity Pt on carbon-black based gas diffusion layers. During the prepa- ration of the mixed Pt-ceria catalyst, hydrogen reduction of CODPtMe 2 to yield Pt catalyzed the deposition of ceria from Ce(tmhd) 4 enabling co-deposition at 150 ◦ C. The catalyst layers were characterized using X- ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and scanning electron microscope-energy dispersive spectral (SEM-EDS) analyses. Their electrochemical performance toward methanol oxidation was examined in half cell mode using a three electrode assembly as well as in fuel cell mode. The thin layer electrodes formed via SFD exhibited higher performance in fuel cell operations compared to those prepared by the conventional brush-paint method. Furthermore, the Pt-ceria catalyst with an optimized composition exhibited greater methanol oxidation activity than pure platinum. © 2012 Elsevier Ltd. All rights reserved. 1. Introduction Low-temperature fuel cells are attractive power sources for portable and vehicular applications. Direct methanol fuel cells (DMFCs) are at the forefront of commercialization due to their favorable characteristics including high energy density, operation at near ambient conditions and low emissions. Moreover, methanol is a renewable fuel source and offers fast and convenient refueling, as it is a liquid from -97.0 to 64.7 ◦ C [1,2]. Despite the attractiveness of DMFCs, hurdles exist in the effec- tive lifetime of the electrodes. Pt, considered to be one of the best catalysts for the DMFCs, suffers from poisoning, especially at the anode side during the methanol electro-oxidation by carbon monoxide (CO) chemisorption, leading to a significant drop in the overall performance [3,4]. Efforts have been made to mitigate CO poisoning by the addition of other metals to platinum such as Ru [5–10], Mo [11,12],W [11,13], Sn [11], Ni [14–16], and Nb [17]. Among these combinations, binary Pt Ru alloys are still considered to be state of the art catalysts for methanol oxidation in DMFCs. The ∗ Corresponding authors. E-mail address: carlos.cabrera2@upr.edu (C.R. Cabrera). addition of transition metal oxides such as MoO x , VO x and WO x to PtRu has also been evaluated for an enhanced methanol oxidation reaction [18–21]. These modified catalysts have been reported to yield a higher methanol oxidation current than the conventional PtRu catalysts. Ruthenium crossover [22], however, has triggered serious concerns about anode stability. Yet another impediment for early DMFC commercialization is the high cost of noble metal catalysts employed in the elec- trodes. Attempts have been made to reduce the catalyst loading by increasing Pt utilization [22–26] using new fabrication methods to enhance the three-phase boundary. The use of non-noble catalysts is another approach for electrode cost reduction. Yu et al. [27] incorporated an oxygen storage mate- rial such as ceria into the cathode catalyst to increase the local oxygen concentration and attained performance enhancement in the DMFC. Xu and Shen [28,29] reported that the electrochemi- cal oxidation of methanol, ethanol, glycerol and ethylene glycol on Pt-CeO 2 /C catalyst constructed in alkaline media showed improved performance compared to conventional Pt/C catalysts. Campos et al. [30] prepared Pt/CeO 2 catalyst layers on a glassy carbon electrode by occlusion deposition method using a bath containing both ceria and K 2 PtCl 6 . An increase in catalytic activity for methanol oxida- tion with the ceria composite electrode was found when compared to the Pt/C system. Yuan et al. [74] reported that carbon nano- 0013-4686/$ – see front matter © 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.electacta.2012.04.091