Electrochimica Acta 56 (2010) 278–284 Contents lists available at ScienceDirect Electrochimica Acta journal homepage: www.elsevier.com/locate/electacta Effect of heat treatment on stability of gold particle modified carbon supported Pt–Ru anode catalysts for a direct methanol fuel cell Xiaowei Li a,∗ , Juanying Liu a , Qinghong Huang a , Walter Vogel b , Daniel L. Akins c , Hui Yang a,∗ a Energy Science and Technology Laboratory, Shanghai Institute of Microsystem and Information Technology, Chinese Academy of Sciences, Shanghai 200050, PR China b Department of Chemistry, National Central University, Taoyuan 32001, Taiwan, ROC c CASI and Department of Chemistry, The City College of The City University of New York, New York 10031, USA article info Article history: Received 18 May 2010 Received in revised form 26 July 2010 Accepted 16 August 2010 Available online 17 September 2010 Keywords: Au nanoparticle Pt–Ru catalyst Methanol oxidation CO stripping Electrocatalytic stability abstract Carbon supported Au–PtRu (Au–PtRu/C) catalysts were prepared as the anodic catalysts for the direct methanol fuel cell (DMFC). The procedure involved simple deposition of Au particles on a commercial Pt–Ru/C catalyst, followed by heat treatment of the resultant composite catalyst at 125, 175 and 200 ◦ C in aN 2 atmosphere. High-resolution transmission electron microscopy (HR-TEM) measurements indicated that the Au nanoparticles were attached to the surface of the Pt–Ru nanoparticles. We found that the electrocatalytic activity and stability of the Au–PtRu/C catalysts for methanol oxidation is better than that of the PtRu/C catalyst. An enhanced stability of the electrocatalyst is observed and attributable to the promotion of CO oxidation by the Au nanoparticles adsorbed onto the Pt–Ru particles, by weakening the adsorption of CO, which can strongly adsorb to and poison Pt catalyst. XPS results show that Au–PtRu/C catalysts with heat treatment lead to surface segregation of Pt metal and an increase in the oxidation state of Ru, which militates against the dissolution of Ru. We additionally find that Au–PtRu/C catalysts heat-treated at 175 ◦ C exhibit the highest electrocatalytic stability among the catalysts prepared by heat treatment: this observation is explained as due to the attainment of the highest relative concentration of gold and the highest oxidation state of Ru oxides for the catalyst pretreated at this temperature. © 2010 Elsevier Ltd. All rights reserved. 1. Introduction The direct methanol fuel cell (DMFC) has become a competitive power source for portable electronic devices because of its high energy density, environmentally nonpolluting products like H 2 O and CO 2 , low operating temperature, and safety in transporting, storing and using the fuel [1,2]. Historically, Pt-based catalysts have been principally used as the anodic catalysts in the DMFC [3–5]. After many years of development, several disadvantages of the DMFC have been generally recognized. One of which is the poor electrocatalytic performance of the anodic Pt-based catalyst—attributable to slow reaction kinetics for methanol oxida- tion reaction (MOR) at the Pt catalyst and the self-poisoning of the Pt catalyst by (CO) ad , an intermediate product of the methanol oxi- dation [6]. A second important performance issue revolves around the fact that when a DMFC operates for an extended period, dis- solution, migration, re-deposition, and aggregation of the metal particles in the catalysts occur and, as a result, the electrocat- alytic performance of the catalysts is reduced. To solve the latter ∗ Corresponding authors. E-mail addresses: xli@ua.pt, lixiaowei76@gmail.com (X. Li), hyang@mail.sim.ac.cn (H. Yang). problem, Pt-based composite catalysts are explored. In particular, Pt–Ru composite catalysts have been found to be among the best for methanol oxidation in DMFCs [7–9]. However, the electrocat- alytic stability of Pt–Ru catalysts is still not adequate for long-term operation of the DMFC, because of the loss of active Pt surface sites and the dissolution of Ru; indeed, the dissolution of Ru occurs more easily than does dissolution of Pt in the fuel cell environment. Early in 1997, He et al. [10] found that the dissolution of Ru can lower the electrocatalytic activity of Pt–Ru anodic catalysts for methanol oxi- dation. Also, recent research indicates that dissolved Ru can migrate through the membrane from the anodic side to the cathodic side during long-term operation [11,12], resulting in lowered cell per- formance [13]. Chen et al. [14] reported that the dissolution of Ru in Pt–Ru catalysts results in an increase in the ohmic resistance and a decrease in the electrocatalytic activity of Pt–Ru catalysts for methanol oxidation. As a result of the above findings, obvious avenues to enhance the electrocatalytic performance of the Pt–Ru catalyst could involve more exotic composite electrocatalysts that avoid the two problems, kinetics and stability. We further note that Zhang et al. [15] have reported that the oxygen-reduction of the Pt catalyst can be stabilized against the dis- solution of Pt by modifying the Pt particles with Au nanoparticles. Also, Chen et al. [16] used an embedded atom method to modify Pt particles with Au; their results suggested that Au atoms adsorbed 0013-4686/$ – see front matter © 2010 Elsevier Ltd. All rights reserved. doi:10.1016/j.electacta.2010.08.083