Electrochimica Acta 50 (2005) 5384–5389 Structure and chemical composition of supported Pt–Sn electrocatalysts for ethanol oxidation Luhua Jiang a,1 , Gongquan Sun a , Shiguo Sun a , Jianguo Liu a , Shuihua Tang a , Huanqiao Li a , Bing Zhou a,b , Qin Xin a,c,∗ a Dalian Institute of Chemical Physics, Direct Alcohol Fuel Cell Group, Zhongshan Road 457, Liaoning Province, Dalian 116023, China b Headwater NanoKinetix Inc., USA c State Key Laboratory of Catalysis, Dalian Institute of Chemical Physics, Graduate School of the Chinese Academy of Sciences, CAS, China Received 22 December 2004; received in revised form 25 February 2005; accepted 4 March 2005 Available online 7 April 2005 Abstract Carbon supported PtSn alloy and PtSnO x particles with nominal Pt:Sn ratios of 3:1 were prepared by a modified polyol method. High resolution transmission electron microscopy (HRTEM) and X-ray microchemical analysis were used to characterize the composition, size, distribution, and morphology of PtSn particles. The particles are predominantly single nanocrystals with diameters in the order of 2.0–3.0 nm. According to the XRD results, the lattice constant of Pt in the PtSn alloy is dilated due to Sn atoms penetrating into the Pt crystalline lattice. While for PtSnO x nanoparticles, the lattice constant of Pt only changed a little. HRTEM micrograph of PtSnO x clearly shows that the change of the spacing of Pt (1 1 1) plane is neglectable, meanwhile, SnO 2 nanoparticles, characterized with the nominal 0.264 nm spacing of SnO 2 (1 0 1) plane, were found in the vicinity of Pt particles. In contrast, the HRTEM micrograph of PtSn alloy shows that the spacing of Pt (1 1 1) plane extends to 0.234 nm from the original 0.226 nm. High resolution energy dispersive X-ray spectroscopy (HR-EDS) analyses show that all investigated particles in the two PtSn catalysts represent uniform Pt/Sn compositions very close to the nominal one. Cyclic voltammograms (CV) in sulfuric acid show that the hydrogen ad/desorption was inhibited on the surface of PtSn alloy compared to that on the surface of the PtSnO x catalyst. PtSnO x catalyst showed higher catalytic activity for ethanol electro-oxidation than PtSn alloy from the results of chronoamperometry (CA) analysis and the performance of direct ethanol fuel cells (DEFCs). It is deduced that the unchanged lattice parameter of Pt in the PtSnO x catalyst is favorable to ethanol adsorption and meanwhile, tin oxide in the vicinity of Pt nanoparticles could offer oxygen species conveniently to remove the CO-like species of ethanolic residues to free Pt active sites. © 2005 Elsevier Ltd. All rights reserved. Keywords: Direct ethanol fuel cell; Electrocatalyst; Pt–Sn; Ethanol electro-oxidation 1. Introduction Bimetallic nanoparticles supported on high surface area carbon find widespread application as electrode materials. Of particular interest is Pt–Sn bimetallic particles used for the electro-oxidation of ethanol at the anode of low temperature ∗ Corresponding author. Tel.: +86 411 84379071; fax: +86 411 84379071. E-mail addresses: sunshine@dicp.ac.cn (L. Jiang), xinqin@dicp.ac.cn (Q. Xin). 1 Tel.: +86 411 4379668; fax: +86 411 4379071. fuel cells [1–9]. Supported Pt–Sn with low loadings (<5%) has been studied well as a catalyst for ethanol or gasoline reforming at high temperature in the past decades [10–13]. However, to the best of our knowledge, few studies on the mi- crochemistry of high loading supported Pt–Sn catalysts em- ployed in low temperature direct ethanol fuel cells has been reported. Preparation procedure strongly affects the disper- sion and the compositional homogeneity of the bimetallic clusters, both of which are important factors in determining their electrocatalytic activity toward ethanol oxidation. In the previous work [7], we have shown that the carbon supported 0013-4686/$ – see front matter © 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.electacta.2005.03.018