title: Synthesis of Pt-Ni Octahedra in Continuous-Flow Droplet Reactors for the Scalable Production of Highly Active Catalysts toward Oxygen Reduction.
abstract: A number of groups have reported the syntheses of nanosized Pt-Ni octahedra with remarkable activities toward the oxygen reduction reaction (ORR), a process key to the operation of proton-exchange membrane fuel cells. However, the throughputs of those batch-based syntheses are typically limited to a scale of 5-25 mg Pt per batch, which is far below the amount needed for commercial evaluation. Here we report the use of droplet reactors for the continuous and scalable production of Pt-Ni octahedra with high activities toward ORR. In a typical synthesis, Pt(acac)2, Ni(acac)2, and W(CO)6 were dissolved in a mixture of oleylamine, oleic acid, and benzyl ether, and then pumped into a polytetrafluoroethylene tube. When the solution entered the reaction zone at a temperature held in the range of 170-230 °C, W(CO)6 quickly decomposed to generate CO gas, naturally separating the reaction solution into discrete, uniform droplets. Each droplet then served as a reactor for the nucleation and growth of Pt-Ni octahedra whose size and composition could be controlled by changing the composition of the solvent and/or adjusting the amount of Ni(acac)2 added into the reaction solution. For a catalyst based on Pt2.4Ni octahedra of 9 nm in edge length, it showed an ORR mass activity of 2.67 A mgPt(-1) at 0.9 V, representing an 11-fold improvement over a state-of-the-art commercial Pt/C catalyst (0.24 A mgPt(-1)).
authors.affiliation: The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University , Atlanta, Georgia 30332, United States.|Key Lab of Organic Optoelectronics and Molecular Engineering of Ministry of Education, Department of Chemistry, Tsinghua University , Beijing 100084, China.
authors.forename: Guangda
authors.initials: G
authors.lastname: Niu
authors.affiliation: The Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University , Atlanta, Georgia 30332, United States.
authors.forename: Ming
authors.initials: M
authors.lastname: Zhou
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: School of Chemistry and Biochemistry, Georgia Institute of Technology , Atlanta, Georgia 30332, United States.
authors.forename: Jinho
authors.initials: J
authors.lastname: Park
authors.affiliation: Department of Materials Science and Engineering, University of Texas at Dallas , Richardson, Texas 75080, United States.
authors.forename: Ning
authors.initials: N
authors.lastname: Lu
authors.affiliation: Department of Materials Science and Engineering, University of Texas at Dallas , Richardson, Texas 75080, United States.
authors.forename: Jinguo
authors.initials: J
authors.lastname: Wang
authors.affiliation: Department of Materials Science and Engineering, University of Texas at Dallas , Richardson, Texas 75080, United States.
authors.forename: Moon J
authors.initials: MJ
authors.lastname: Kim
authors.affiliation: Key Lab of Organic Optoelectronics and Molecular Engineering of Ministry of Education, Department of Chemistry, Tsinghua University , Beijing 100084, China.
authors.forename: Liduo
authors.initials: L
authors.lastname: Wang
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, Georgia Institute of Technology , Atlanta, Georgia 30332, United States.
authors.forename: Younan
authors.initials: Y
authors.lastname: Xia
keywords: Pt−Ni octahedra; continuous production; droplet reactors; oxygen reduction reaction; scale up