Single Phase PtAg Bimetallic Alloy Nanoparticles Highly Dispersed on Reduced Graphene Oxide for Electrocatalytic Application of Methanol Oxidation Reaction Ammar Bin Yousaf 1 , Muhammad Imran 1 , Akif Zeb, Tao Wen, Xiao Xie, Yi-Fan Jiang, Cheng-Zong Yuan, An-Wu Xu* Division of Nanomaterials and Chemistry, Hefei National Laboratory for Physical Sciences at Microscale, University of Science and Technology of China, Hefei, Anhui 230026, PR China A R T I C L E I N F O Article history: Received 28 October 2015 Received in revised form 5 March 2016 Accepted 10 March 2016 Available online 11 March 2016 Keywords: bimetallic nanocomposite reduced graphene oxide anode material electrocatalysis methanol oxidation reaction A B S T R A C T As renewable materials having high specific energy and environmentally safe characteristics, direct methanol fuel cells (DMFCs) have attracted huge interest to develop promising power devices with different strategies. Herein, single phase PtAg bimetallic alloy highly dispersed electrocatalyst on reduced graphene oxide (rGO) by a facile wet chemical co-reduction method. Different kinds of catalysts have been prepared with varying atomic ratios of Pt and Ag. Structural and morphological characterizations of as-synthesized catalysts are performed by transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM) and X-ray diffraction (XRD) and X-ray photoelectron diffraction (XPS) analysis. It is found that single phase PtAg bimetallic nanoparticles are successfully synthesized that are uniformly dispersed and attached on rGO sheets. High-angle annular dark-field scaning TEM (HAADF-STEM) and energy dispersive X-ray spectroscopic (EDX) analysis have also been performed, which confirm the single phase synthesis of uniformly dispersed PtAg bimetallic catalyst. MOR activity and durability has significantly increased by mutual coordination of both the metals in bimetallic nanocatalyst in comparison with the monometallic commercial Pt/C catalyst. The results can be attributed to the collective effects of the PtAg nanoparticles and the enhanced electron transfer characteristics of rGO sheets. ã 2016 Elsevier Ltd. All rights reserved. 1. Introduction The direct methanol fuel cells (DMFCs) have attracted much attention in the past few decades as green power sources due to its important application as methanol electro-oxidationreaction(MOR) [1]. Up to now, Pt showed strongest candidate as anode material for DMFCs due to its highest electrocatalytic activity for MOR among monometallic catalysts [2–4]. However, there are much complica- tions being faced by using monometallic Pt catalysts regarding its easy poisoning by intermediate species such as CO ads during MOR process, which further leads to the deactivation of the catalysts [5,6]. Since past several years, a number of modifications and studies have been devoted to bimetallic alloys with Pt, due to the fact that the electronic effects enhance electrocatalytic performance and CO tolerance in MOR for these materials in comparison to Pt monometallic anodes [7]. The search for alternative catalysts with tunable composition (bi or tri metallic composites) and performance regarding cost-effect is still a critical issue and major research highlight for fuel cell systems [8,9]. With the literature evidences it has been shown that alloys of Pt with less expensive elements such as Ag, Au and other transition metals is an effective strategy to overcome the problems with existing materials, some of them being higher performance and lower cost of DMFCs [10–14]. The electro- catalytic characteristics of metal alloy nanomaterials are highly dependent on size and composition [15]. Due to this reason, an accurate intrinsic correlation of alloy particle composition with catalytic activity requires the availability of vigorous and preferably facile preparation routes that can provide independent control over the challenges faced in synthesis [16]. Practically, all physical or wet- chemical alloy synthetic techniques reported till date have failed to independently and precisely control the size and composition. Therefore, pragramatic trial and error procedures are still required to arrive at desired size or composition values [17]. * Corresponding author. E-mail address: anwuxu@ustc.edu.cn (A.-W. Xu). 1 These two authors contributed equally to this work. http://dx.doi.org/10.1016/j.electacta.2016.03.067 0013-4686/ ã 2016 Elsevier Ltd. All rights reserved. Electrochimica Acta 197 (2016) 117–125 Contents lists available at ScienceDirect Electrochimica Acta journa l home page : www.e lsevier.com/loca te/ele cta cta