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2.
Nat Mater ; 19(11): 1207-1214, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32690912

RESUMO

A remaining challenge for the deployment of proton-exchange membrane fuel cells is the limited durability of platinum (Pt) nanoscale materials that operate at high voltages during the cathodic oxygen reduction reaction. In this work, atomic-scale insight into well-defined single-crystalline, thin-film and nanoscale surfaces exposed Pt dissolution trends that governed the design and synthesis of durable materials. A newly defined metric, intrinsic dissolution, is essential to understanding the correlation between the measured Pt loss, surface structure, size and ratio of Pt nanoparticles in a carbon (C) support. It was found that the utilization of a gold (Au) underlayer promotes ordering of Pt surface atoms towards a (111) structure, whereas Au on the surface selectively protects low-coordinated Pt sites. This mitigation strategy was applied towards 3 nm Pt3Au/C nanoparticles and resulted in the elimination of Pt dissolution in the liquid electrolyte, which included a 30-fold durability improvement versus 3 nm Pt/C over an extended potential range up to 1.2 V.

3.
Nano Lett ; 11(3): 919-26, 2011 Mar 09.
Artigo em Inglês | MEDLINE | ID: mdl-20704335

RESUMO

We report the design and synthesis of multimetallic Au/Pt-bimetallic nanoparticles as a highly durable electrocatalyst for the oxygen reduction reaction (ORR) in proton exchange membrane fuel cells. This system was first studied on well-defined Pt and FePt thin films deposited on a Au(111) surface, which has guided the development of novel synthetic routes toward shape-controlled Au nanoparticles coated with a Pt-bimetallic alloy. It has been demonstrated that these multimetallic Au/FePt(3) nanoparticles possess both the high catalytic activity of Pt-bimetallic alloys and the superior durability of the tailored morphology and composition profile, with mass-activity enhancement of more than 1 order of magnitude over Pt catalysts. The reported synergy between well-defined surfaces and nanoparticle synthesis offers a persuasive approach toward advanced functional nanomaterials.

4.
J Am Chem Soc ; 132(18): 6524-9, 2010 May 12.
Artigo em Inglês | MEDLINE | ID: mdl-20397665

RESUMO

Rational synthesis of Pt-Au(n) nanoparticles (NPs) has been achieved by overgrowing Au on Pt with n, the number of Pt-Au heterojunctions in each particle, controlled from 1 to 4, and the corresponding NPs in pear-, peanut-, or clover-like morphology. Monte Carlo simulation reveals that the morphology control can be correlated to a thermodynamic equilibrium of the Au coherence energy, the overall particle surface energy, and the heterogeneous Pt-Au interfacial energy in the composite system, which is manipulated by the seeding particle size and solvent polarity. The developed synthetic strategy together with the provided fundamental understanding of heterogeneous nucleation and heterostructure growth could have great potential toward the rational synthesis of composite nanomaterials with morphology control for advanced catalytic and other functional applications.


Assuntos
Ouro/química , Nanopartículas Metálicas/química , Platina/química , Catálise , Eletroquímica , Análise de Fourier , Metanol/química , Microscopia Eletrônica de Transmissão , Método de Monte Carlo , Oxirredução , Tamanho da Partícula , Solventes/química
5.
Nano Lett ; 9(4): 1493-6, 2009 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-19260706

RESUMO

Monodisperse dumbbell-like Pt-Fe(3)O(4) nanoparticles are synthesized by epitaxial growth of Fe onto Pt nanoparticles followed by Fe oxidation. The nanoparticle size in the structure is tunable from 2 to 8 nm for Pt and 6 to 20 nm for Fe(3)O(4). Pt nanoparticles in the Pt-Fe(3)O(4) structure show a 20-fold increase in mass activity toward oxygen reduction reaction compared with the single component Pt nanoparticles and the commercial 3 nm Pt particles. The work proves that it is possible to maximize catalytic activity of the Pt nanoparticle catalyst through the control not only of Pt size and shape but also of its interaction with Fe(3)O(4) nanoparticles.

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