Electrochimica Acta 123 (2014) 309–316 Contents lists available at ScienceDirect Electrochimica Acta jo u r n al hom ep age: www.elsevier.com/locate/electacta Highly active Pt-on-Au catalysts for methanol oxidation in alkaline media involving a synergistic interaction between Pt and Au Jianshe Wang a,∗ , Ranran Shi a , Xun Guo b , Jingyu Xi c,∗ , Jianhong Zhao a , Chengying Song a , Liucheng Wang a , Jiujun Zhang d a School of Chemical Engineering and Energy, Zhengzhou University, Zhengzhou 450000, PR China b Department of Chemistry, Tsinghua University, Beijing 100086, PR China c Lab of Advanced Power Sources and Key Laboratory of Thermal Management Engineering and Materials, Graduate School at Shenzhen, Tsinghua University, Shenzhen 518055, PR China d National Research Council of Canada, Vancouver, BC, V6T 1W5, Canada a r t i c l e i n f o Article history: Received 9 October 2013 Received in revised form 6 January 2014 Accepted 7 January 2014 Available online 21 January 2014 Keywords: Pt-on-Au catalysts Site-selective electrodeposition Methanol oxidation reaction Synergism a b s t r a c t Several Pt-on-Au/SnO 2 -CNTs catalysts with different Pt loadings are synthesized through site-selective electrodeposition for catalytic methanol oxidation reaction (MOR) in alkaline media. The catalysts are tested to exhibit extremely high Pt mass activity towards MOR, and the catalytic mechanism is proposed based on the synergetic effect between Pt and Au, in which the Pt entities provide Pt-OH for oxidation of alkoxide (CH 3 O - ) while the Au surfaces provide adsorption sites for alkoxide. It is expected that this mechanism could be extended to developing high performance non-Pt catalysts for MOR in alkaline media. © 2014 Elsevier Ltd. All rights reserved. 1. Introduction In recent years, anion-exchange membrane direct alcohol fuel cells have attracted great attentions due to their several advan- tages including the fast kinetics of both alcohol (methanol and ethanol for example) oxidation and oxygen reduction reactions in alkaline media, and the promising potential to use non-Pt metal catalysts [1–3]. Regarding the methanol oxidation reaction (MOR) in alkaline media, various non-Pt catalysts such as Pd [4], Au [5], Ag [6], PdAg[7], AuRh[8], PdCu[9] have been developed. However, the fundamental understanding of the MOR catalysis mechanism in alkaline media still seems insufficient for guiding the development. Therefore, at the current state of technology, the catalyst develop- ments are largely relied on the trial-and-error approaches. With respect to this, clarifying the structure-performance correlation of the MOR catalysts is quite necessary for rational catalyst designing. Since Pt component has been most widely studied in electrocatal- ysis [10–13], it seems wise and reasonable to study Pt-containing catalysts and their associated MOR mechanism, and then use the understanding to guide the design of non-Pt catalysts. ∗ Corresponding author. Tel.: +86 0371 6778 1027; fax: +86 0371 6778 1027. E-mail addresses: wangjs07@zzu.edu.cn (J. Wang), xijingyu@gmail.com (J. Xi). Recently, Pt-on-Au catalysts [14–17] have attracted intensive attention due to their high Pt utilization and high Pt mass activ- ity in certain cases, for example, HCOOH oxidation in acid media. However, reports on the MOR on the Pt-on-Au catalysts in alka- line media are quite limited. Most recently, we prepared several highly active Pt-on-Au catalysts supported on SnO 2 and CNTs (car- bon nanotubes) composite material (these catalysts are expressed abbreviately as Pt-on-Au/SnO 2 -CNTs) with quite low Pt contents for HCOOH oxidation reaction [18]. When testing the MOR activity on the as-prepared Pt-on-Au/SnO 2 -CNTs catalysts in alkaline media, extremely high activity (∼220 A mg Pt -1 ) was obtained. As a con- tinuing study, in this paper, the synergetic effect between Pt and Au was observed, based on which the possible MOR mechanism catalyzed by Pt-on-Au/SnO 2 -CNTs catalysts was proposed through analyzing the experimental observation and the data observed. We believe that the results presented in this paper could be beneficial to the development of high-performance non-Pt catalysts for MOR in alkaline media. 2. Experimental The preparation and the structural characterization of com- posite support (Au/SnO 2 -CNTs) and Pt-on-Au/SnO 2 -CNTs have been reported elsewhere [18]. For preparation of Au/SnO 2 -CNTs, Au nanoparticles were formed through reduction of NaAuCl 4 by 0013-4686/$ – see front matter © 2014 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.electacta.2014.01.044