title: Nucleation and growth mechanism of Pd/Pt bimetallic clusters in sodium bis(2-ethylhexyl)sulfosuccinate (AOT) reverse micelles as studied by in situ X-ray absorption spectroscopy.
abstract: We report in situ X-ray absorption spectroscopy (XAS) investigations on the formation of palladium-platinum (Pd/Pt) bimetallic clusters at the early stage within the water-in-oil microemulsion system of water/AOT/n-heptane. The reduction of palladium and platinum ions and the formation of corresponding clusters are monitored as a function of dosage of reducing agent, hydrazine (N(2)H(5)OH). Upon successive addition of the reducing agent, hydrazine (N(2)H(5)OH), five distinguishable steps are observed in the formation process of Pd/Pt clusters at the early stage. Both in situ X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) analysis for both the Pd K-edge and Pt L(III)-edge revealed the formation of Pd/Pt bimetallic clusters. A corresponding structural model is proposed for each step to provide a detailed insight into the nucleation and growth mechanism of Pd/Pt bimetallic clusters. We also discussed the atomic distribution of Pd and Pt atoms in Pd/Pt bimetallic clusters based on the calculated XAS structural parameters.
authors.affiliation: Nanoelectrochemistry Laboratory, Department of Chemical Engineering, National Taiwan University of Science and Technology, Taipei 106, Taiwan, R.O.C.
authors.forename: Ching-Hsiang
authors.initials: CH
authors.lastname: Chen
authors.forename: Bing-Joe
authors.initials: BJ
authors.lastname: Hwang
authors.forename: Guo-Rung
authors.initials: GR
authors.lastname: Wang
authors.forename: Loka Subramanyam
authors.initials: LS
authors.lastname: Sarma
authors.forename: Mau-Tsu
authors.initials: MT
authors.lastname: Tang
authors.forename: Din-Goa
authors.initials: DG
authors.lastname: Liu
authors.forename: Jyh-Fu
authors.initials: JF
authors.lastname: Lee
mesh_terms: D004143:Dioctyl Sulfosuccinic Acid / Q000737:chemistry*; D008823:Micelles; D009942:Organometallic Compounds / Q000138:chemical synthesis* / Q000737:chemistry; D010165:Palladium / Q000737:chemistry*; D010984:Platinum / Q000737:chemistry*; D012680:Sensitivity and Specificity; D013057:Spectrum Analysis / Q000379:methods; D014965:X-Rays
chemical_list: D008823:Micelles; D009942:Organometallic Compounds; D004143:Dioctyl Sulfosuccinic Acid; D010984:Platinum; D010165:Palladium