Synthesis of Bimetallic AuPt Nanoparticles in Aqueous Solution and Electrocatalytic Activity
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0900-O13-07.1
Synthesis of Bimetallic AuPt Nanoparticles in Aqueous Solution and Electrocatalytic Activity Peter N. Njoki, Jin Luo, Aisley Jacob, Rizwan Munawar, Bilal Khan and Chuan-Jian Zhong* Department of Chemistry, State University of New York at Binghamton, Binghamton, New York 13902, USA. * [email protected]
ABSTRACT The ability to control composition and size in the synthesis of bimetallic nanoparticles is important for the exploitation of the bimetallic catalytic properties. This paper reports recent findings of an investigation of the synthesis of gold-platinum (AuPt) bimetallic nanoparticles in aqueous solution via reduction of AuCl4- and PtCl4 2- using a combination of reducing and capping agents. In addition to characterization of the morphological properties of the AuPt nanoparticles using TEM and XRD, the electrocatalytic activity of the carbon-supported AuPt nanoparticle catalysts was also examined for oxygen reduction reaction (ORR) using the rotating disk electrode (RDE) technique. The findings have implications to the design of bimetallic nanoparticle catalysts for fuel cell reactions.
INTRODUCTION The exploration of effective methods for the preparation of gold and gold-based alloy nanoparticle catalysts is important for achieving the desired or bifunctional catalytic activities for a variety of oxidation or reduction reactions [1]. Such exploration requires the ability to control the composition and size of bimetallic nanoparticles. The two-phase synthesis of organic-soluble Au and AuPt nanoparticles [2-8] was recently utilized for the preparation of nanoparticle catalysts for the electrocatalytic reactions [9-11]. In order to develop effective and controllable methods for the preparation of bimetallic nanoparticles and the effective catalyst dispersion on support materials, it is often desired to prepare and process catalyst nanoparticles with appropriate solubilities in the desired solvents, which can be subsequently dispersed and loaded onto different support materials. In this paper, we report recent findings of an investigation of the synthesis of AuPt nanoparticles in aqueous solution based on a combination of reducing and capping agents (Scheme 1) [12], and the electrocatalytic activity of the bimetallic nanoparticles for oxygen reduction reaction. In the synthesis, hydrogen served as reducing agent for the reduction of Pt(II), whereas acrylate functioned as reducing agent for the reduction of Au(III) in the presence of the catalytic effect of Pt as a result of the reduction of Pt(II). This approach is demonstrated to be highly effective for the preparation of gold-platinum nanoparticles with controllable composition and sizes. The bimetallic nanoparticles are shown to be electrocatalytically active for oxygen reduction reaction.
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Scheme 1. A schematic illustration for the synthesis of capped AuPt nanoparticles
EXPERIMENTAL Potassium tetrachloroplatinate, (K2PtCl4, 99.99%), hydrogen tetrachloroaurate (HAuCl4, 99%), sodium acrylate (H2C=CHCO2Na, A, 97%), were purch
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