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Journal ArticleDOI

One-pot synthesis of three-dimensional platinum nanochain networks as stable and active electrocatalysts for oxygen reduction reactions

Jiangfeng Xu1, Gengtao Fu1, Yawen Tang1, Yiming Zhou1, Yu Chen1, Tianhong Lu1 
19 Jun 2012-Journal of Materials Chemistry (The Royal Society of Chemistry)-Vol. 22, Iss: 27, pp 13585-13590
TL;DR: In this paper, three-dimensional platinum nanochain network (Pt-3NCNW) nanostructures are synthesized through a thermal decomposition method using platinum(IV)-complexes as reaction precursors in the absence of surfactants and templates.
Abstract: Three-dimensional platinum nanochain network (Pt-3NCNW) nanostructures are synthesized through a thermal decomposition method using platinum(IV)-complexes as reaction precursors in the absence of surfactants and templates. The size, morphology and surface composition of Pt-3NCNWs are investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). These spectral studies confirm the as-papered products are three-dimensionally interconnected network nanostructures with primary Pt nanochains as building blocks, and the Pt nanochains grow from the primary spheric Pt nanoparticles via oriented attachment. Compared to the commercial Pt black catalyst, the Pt-3NCNW nanostructures exhibit superior electrocatalytic activity and stability towards oxygen reduction reactions, which is ascribed to their unique properties such as the few surface defect sites and the low hydroxyl surface coverage on one-dimensional Pt nanochains, as well as fast O2 diffusion in three-dimensional structures.
Citations
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Journal Article
TL;DR: In this article, the authors used in situ transmission electron microscopy to show that platinum nanocrystals can grow either by monomer attachment from solution onto the existing particles or by coalescence between the particles.
Abstract: It is conventionally assumed that the growth of monodisperse colloidal nanocrystals requires a temporally discrete nucleation followed by monomer attachment onto the existing nuclei. However, recent studies have reported violations of this classical growth model, and have suggested that inter-particle interactions are also involved during the growth. Mechanisms of nanocrystal growth still remain controversial. Using in situ transmission electron microscopy, we show that platinum nanocrystals can grow either by monomer attachment from solution onto the existing particles or by coalescence between the particles. Surprisingly, an initially broad size distribution of the nanocrystals can spontaneously narrow. We suggest that nanocrystals take different pathways of growth based on their size- and morphology-dependent internal energies. These observations are expected to be highly relevant for other nanocrystal systems.

949 citations

Journal ArticleDOI
TL;DR: In this Critical Review, recent advances in optimizing both cathode materials and PEMs as well as the future and peculiar challenges associated with each of these systems will be discussed.
Abstract: The rising interest in fuel cell vehicle technology (FCV) has engendered a growing need and realization to develop rational chemical strategies to create highly efficient, durable, and cost-effective fuel cells. Specifically, technical limitations associated with the major constituent components of the basic proton exchange membrane fuel cell (PEMFC), namely the cathode catalyst and the proton exchange membrane (PEM), have proven to be particularly demanding to overcome. Therefore, research trends within the community in recent years have focused on (i) accelerating the sluggish kinetics of the catalyst at the cathode and (ii) minimizing overall Pt content, while simultaneously (a) maximizing activity and durability as well as (b) increasing membrane proton conductivity without causing any concomitant loss in either stability or as a result of damage due to flooding. In this light, as an example, high temperature PEMFCs offer a promising avenue to improve the overall efficiency and marketability of fuel cell technology. In this Critical Review, recent advances in optimizing both cathode materials and PEMs as well as the future and peculiar challenges associated with each of these systems will be discussed.

273 citations

Journal ArticleDOI
Gengtao Fu1, Ke Wu1, Jun Lin1, Yawen Tang1, Yu Chen1, Yiming Zhou1, Tianhong Lu1 
TL;DR: In this paper, the Pt-Pd alloy nanoflowers with dominant 111 facets were successfully synthesized through a facile cochemical reduction method in a poly(allylamine hydrochloride) (PAH) based aqueous solution, and detailed morphology, composition, and structure of the Pt -Pd ANFs were investigated by transmission electron microscopy (TEM), selected-area electron diffraction (SAED), energy dispersive spectrum (EDS), nitrogen adsorption-desorption isotherms (SADI), EDS
Abstract: Well-defined and strikingly monomorphic Pt–Pd alloy nanoflowers (Pt–Pd ANFs) with dominant {111} facets were successfully synthesized through a facile cochemical reduction method in a poly(allylamine hydrochloride) (PAH) based aqueous solution. The detailed morphology, composition, and structure of the Pt–Pd ANFs were investigated by transmission electron microscopy (TEM), selected-area electron diffraction (SAED), energy dispersive spectrum (EDS), nitrogen adsorption–desorption isotherms (SADI), EDS mapping, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS), demonstrating the Pt–Pd ANFs were highly porous and a self-supported structure. The formation mechanism of the Pt–Pd ANFs were investigated by TEM and Fourier transform infrared (FT-IR), indicating that the existence of PAH and rapid growth of crystal nuclei were essential for the formation of the Pt–Pd ANFs. The electrocatalytic activity and stability of the Pt–Pd ANFs for the oxygen reduction reaction (ORR) were investigated by ro...

235 citations

Journal ArticleDOI
TL;DR: In this article, the most recent progress on the solvothermal syntheses and applications of metal nanocrystals are discussed, including temperature, reaction time, solvent effects, ligand effects, facet-specific capping agent effects, and reductant effects.

189 citations

Journal ArticleDOI
TL;DR: The synthesis of platinum-copper bimetallic alloy nanodendrites (Pt-Cu BANDs) by a facile, one-pot, templateless, and seedless hydrothermal method in the presence of poly(allylamine hydrochloride) (PAH) and formaldehyde (HCHO) shows higher electrocatalytic activity and stability than commercially available Pt black.
Abstract: The controllable synthesis of noble metal alloy nanostructures with highly branched morphology has attracted much attention because of their specific physical and chemical properties. This article reports the synthesis of platinum–copper bimetallic alloy nanodendrites (Pt–Cu BANDs) by a facile, one-pot, templateless, and seedless hydrothermal method in the presence of poly(allylamine hydrochloride) (PAH) and formaldehyde (HCHO). The morphology, composition, and structure of Pt–Cu BANDs are fully characterized by various physical techniques, demonstrating Pt–Cu BANDs are highly alloying, porous, and self-supported nanostructures. The formation/growth mechanism of Pt–Cu BANDs is explored and discussed based on the experimental observations. The autocatalytic growth and interdiffusion are responsible for the formation of Pt–Cu alloy whereas selective oxidative etching results in dendritic morphology of Pt–Cu alloy nanostructures. In addition, the electrocatalytic activity and stability of Pt–Cu BANDs for the...

165 citations

References
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Journal ArticleDOI
05 Jun 2009-Science
TL;DR: Pd-Pt bimetallic nanodendrites consisting of a dense array of Pt branches on a Pd core by reducing K2PtCl4 with L-ascorbic acid in the presence of uniform Pd nanocrystal seeds in an aqueous solution showed relatively large surface areas and particularly active facets toward the oxygen reduction reaction (ORR), the rate-determining step in a proton-exchange membrane fuel cell.
Abstract: Controlling the morphology of Pt nanostructures can provide a great opportunity to improve their catalytic properties and increase their activity on a mass basis. We synthesized Pd-Pt bimetallic nanodendrites consisting of a dense array of Pt branches on a Pd core by reducing K2PtCl4 with L-ascorbic acid in the presence of uniform Pd nanocrystal seeds in an aqueous solution. The Pt branches supported on faceted Pd nanocrystals exhibited relatively large surface areas and particularly active facets toward the oxygen reduction reaction (ORR), the rate-determining step in a proton-exchange membrane fuel cell. The Pd-Pt nanodendrites were two and a half times more active on the basis of equivalent Pt mass for the ORR than the state-of-the-art Pt/C catalyst and five times more active than the first-generation supportless Pt-black catalyst.

2,695 citations

Journal ArticleDOI
28 Jun 1996-Science
TL;DR: Tetrahedral, cubic, irregular-prismatic, icosahedral, and cubo-octahedral particle shapes were observed, whose distribution was dependent on the concentration ratio of the capping polymer material to the platinum cation.
Abstract: The shapes and sizes of platinum nanoparticles were controlled by changes in the ratio of the concentration of the capping polymer material to the concentration of the platinum cations used in the reductive synthesis of colloidal particles in solution at room temperature. Tetrahedral, cubic, irregular-prismatic, icosahedral, and cubo-octahedral particle shapes were observed, whose distribution was dependent on the concentration ratio of the capping polymer material to the platinum cation. Controlling the shape of platinum nanoparticles is potentially important in the field of catalysis.

2,305 citations

Journal ArticleDOI
TL;DR: In this article, the authors present a consistent picture of some key physical properties determining the reactivity of metal and alloy surfaces, and suggest that trends in reactivities can be understood in terms of the hybridization energy between the bonding and anti-bonding adsorbate states and the metal d-bands (when present).

2,008 citations

Journal ArticleDOI
TL;DR: In this article, self-consistent density functional calculations for the adsorption of O and CO, and the dissociation of CO on strained and unstrained Ru(0001) surfaces are used to show how strained metal surfaces have chemical properties that are significantly different from those of un-strained surfaces.
Abstract: Self-consistent density functional calculations for the adsorption of O and CO, and the dissociation of CO on strained and unstrained Ru(0001) surfaces are used to show how strained metal surfaces have chemical properties that are significantly different from those of unstrained surfaces. Surface reactivity increases with lattice expansion, following a concurrent up-shift of the metal $d$ states. Consequences for the catalytic activity of thin metal overlayers are discussed.

1,905 citations

Journal ArticleDOI
12 Jan 2007-Science
TL;DR: It is demonstrated that platinum (Pt) oxygen-reduction fuel-cell electrocatalysts can be stabilized against dissolution under potential cycling regimes by modifying Pt nanoparticles with gold (Au) clusters, and data suggest that the Au clusters confer stability by raising the Pt oxidation potential.
Abstract: We demonstrated that platinum (Pt) oxygen-reduction fuel-cell electrocatalysts can be stabilized against dissolution under potential cycling regimes (a continuing problem in vehicle applications) by modifying Pt nanoparticles with gold (Au) clusters. This behavior was observed under the oxidizing conditions of the O2 reduction reaction and potential cycling between 0.6 and 1.1 volts in over 30,000 cycles. There were insignificant changes in the activity and surface area of Au-modified Pt over the course of cycling, in contrast to sizable losses observed with the pure Pt catalyst under the same conditions. In situ x-ray absorption near-edge spectroscopy and voltammetry data suggest that the Au clusters confer stability by raising the Pt oxidation potential.

1,652 citations