《Biphasic Pd-Au Alloy Catalyst for Low-Temperature》.pdf

Published on Web 07/13/2010 Biphasic Pd-Au Alloy Catalyst for Low-Temperature CO Oxidation Jing Xu,† Tim White,‡ Ping Li,† Chongheng He,† Jianguo Yu,† Weikang Yuan,† and Yi-Fan Han*,† State Key Laboratory of Chemical Engineering, East China UniVersity of Science and Technology, Shanghai 200237, People’s Republic of China, and Centre for AdVanced Microcopy, Australian National Uni Versity, Canberra, ACT 2601, Australia Received March 30, 2010; E-mail: yifanhan@ecust.edu.cn Abstract: Low-temperature CO oxidation over a compositional series of Pd-Au nanoalloy catalysts supported on silica fume was studied. Except for the pure metals, these materials invariably showed biphasic separation into palladium- and gold-rich components. Performance was optimal for a catalyst of bulk composition Pd Au , a mixture of Pd Au (72.5 at. %) and Pd Au (27.5 at. %), that was remarkably 4 1 90 10 31 69 active at 300 K and more stable than a pure Au catalyst. For bulk materials dominated by Pd (Pd:Au ) 16:1; 8:1; 4:1), the palladium-rich alloy fraction frequently adopted hollow sphere or annular morphology, while the gold-rich crystals were often multiply twinned. Quantitative powder X-ray diffraction (XRD) showed that under the synthesis conditions used, the Au solubility limi