title: Synthesis and Characterization of Pt-Ag Alloy Nanocages with Enhanced Activity and Durability toward Oxygen Reduction.
abstract: Engineering the elemental composition of metal nanocrystals offers an effective strategy for the development of catalysts or electrocatalysts with greatly enhanced activity. Herein, we report the synthesis of Pt-Ag alloy nanocages with an outer edge length of 18 nm and a wall thickness of about 3 nm. Such nanocages with a composition of Pt19Ag81could be readily prepared in one step through the galvanic replacement reaction between Ag nanocubes and a Pt(II) precursor. After 10 000 cycles of potential cycling in the range of 0.60-1.0 V as in an accelerated durability test, the composition of the nanocages changed to Pt56Ag44, together with a specific activity of 1.23 mA cm-2toward oxygen reduction, which was 3.3 times that of a state-of-the-art commercial Pt/C catalyst (0.37 mA cm-2) prior to durability testing. Density functional theory calculations attributed the increased activity to the stabilization of the transition state for breaking the O-O bond in molecular oxygen. Even after 30 000 cycles of potential cycling, the mass activity of the nanocages only dropped from 0.64 to 0.33 A mg-1Pt, which was still about two times that of the pristine Pt/C catalyst (0.19 A mg-1Pt).
authors.affiliation: The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University , Atlanta, Georgia 30332, United States.
authors.forename: Xuan
authors.initials: X
authors.lastname: Yang
authors.affiliation: Department of Chemical and Biological Engineering, University of Wisconsin-Madison , Madison, Wisconsin 53706, United States.
authors.forename: Luke T
authors.initials: LT
authors.lastname: Roling
authors.affiliation: School of Chemistry and Biochemistry, School of Chemical and Biomolecular Engineering, Georgia Institute of Technology , Atlanta, Georgia 30332, United States.
authors.forename: Madeline
authors.initials: M
authors.lastname: Vara
authors.affiliation: Department of Chemical and Biological Engineering, University of Wisconsin-Madison , Madison, Wisconsin 53706, United States.
authors.forename: Ahmed O
authors.initials: AO
authors.lastname: Elnabawy
authors.affiliation: School of Chemistry and Biochemistry, School of Chemical and Biomolecular Engineering, Georgia Institute of Technology , Atlanta, Georgia 30332, United States.
authors.forename: Ming
authors.initials: M
authors.lastname: Zhao
authors.affiliation: School of Chemistry and Biochemistry, School of Chemical and Biomolecular Engineering, Georgia Institute of Technology , Atlanta, Georgia 30332, United States.|Center for Nanophase Materials Sciences, Oak Ridge National Laboratory , Oak Ridge, Tennessee 37831, United States.
authors.forename: Zachary D
authors.initials: ZD
authors.lastname: Hood
authors.affiliation: The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University , Atlanta, Georgia 30332, United States.
authors.forename: Shixiong
authors.initials: S
authors.lastname: Bao
authors.affiliation: Department of Chemical and Biological Engineering, University of Wisconsin-Madison , Madison, Wisconsin 53706, United States.
authors.forename: Manos
authors.initials: M
authors.lastname: Mavrikakis
authors.affiliation: The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University , Atlanta, Georgia 30332, United States.|School of Chemistry and Biochemistry, School of Chemical and Biomolecular Engineering, Georgia Institute of Technology , Atlanta, Georgia 30332, United States.
authors.forename: Younan
authors.initials: Y
authors.lastname: Xia
keywords: Pt−Ag alloy; density functional theory; nanocage; oxygen reduction reaction; platinum-based catalyst