title: Controlling the size and composition of nanosized Pt-Ni octahedra to optimize their catalytic activities toward the oxygen reduction reaction.
abstract: Electrocatalysts based on Pt-Ni alloys have received considerable interest in recent years owing to their remarkable activities toward the oxygen reduction reaction (ORR). Here, we report the synthesis of nanosized Pt-Ni octahedra with a range of controlled sizes and compositions in an effort to optimize their ORR activities. If we employed benzyl ether as a solvent for the synthesis, we could readily control the edge lengths of the Pt-Ni octahedra in the range of 6-12 nm and keep the Pt/Ni atomic ratio at around 2.4 by varying the amount of oleylamine added into the reaction system. If we adjusted the amount of Ni precursor, the atomic ratio of Pt to Ni in the Pt-Ni octahedra could be controlled in the range of 1.4-3.7 and their edge lengths were kept at 9 nm. For the catalysts with a Pt/Ni atomic ratio around 2.4, their specific ORR activities (per unit surface area) increased monotonically as the edge length increased from 6 to 12 nm. However, the mass activities (per unit mass of Pt) of these Pt-Ni octahedra showed a maximum value at an edge length of 9 nm. The specific and mass activities for the Pt-Ni octahedra with an edge length of 9 nm but different compositions both showed peak values at a Pt/Ni atomic ratio of 2.4.
authors.affiliation: The Wallace H. Coulter Department of Biomedical Engineering, School of Chemistry and Biochemistry and School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332 (USA).
authors.forename: Sang-Il
authors.initials: SI
authors.lastname: Choi
authors.forename: Shuifen
authors.initials: S
authors.lastname: Xie
authors.forename: Minhua
authors.initials: M
authors.lastname: Shao
authors.forename: Ning
authors.initials: N
authors.lastname: Lu
authors.forename: Sandra
authors.initials: S
authors.lastname: Guerrero
authors.forename: Jonathan H
authors.initials: JH
authors.lastname: Odell
authors.forename: Jinho
authors.initials: J
authors.lastname: Park
authors.forename: Jinguo
authors.initials: J
authors.lastname: Wang
authors.forename: Moon J
authors.initials: MJ
authors.lastname: Kim
authors.forename: Younan
authors.initials: Y
authors.lastname: Xia
mesh_terms: D000497:Alloys / Q000737:chemistry*; D002384:Catalysis; D055664:Electrochemical Techniques; D053768:Metal Nanoparticles / Q000737:chemistry*; D046529:Microscopy, Electron, Transmission; D009532:Nickel / Q000737:chemistry*; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry*; D010316:Particle Size; D010984:Platinum / Q000737:chemistry*; D013499:Surface Properties; D014961:X-Ray Diffraction
chemical_list: D000497:Alloys; D010984:Platinum; D009532:Nickel; D010100:Oxygen
keywords: catalysis; fuel cells; nickel; oxygen; platinum