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Platinum

About: Platinum is a research topic. Over the lifetime, 49675 publications have been published within this topic receiving 1150035 citations. The topic is also known as: Pt & element 78.


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Journal ArticleDOI
TL;DR: In this paper, a variety of synthetic approaches are employed to shed light on the influence of nanoparticle agglomeration on their electrocatalytic properties, showing that the reaction is strongly size sensitive, exhibiting an increase of the reaction overpotential as the particle size decreases below ca. 3 nm.
Abstract: Fuel cell electrocatalysts usually feature high noble metal contents, and these favour particle agglomeration. In this paper a variety of synthetic approaches (wet chemical deposition, electrodeposition and electrodeposition on chemically preformed Pt nuclei) is employed to shed light on the influence of nanoparticle agglomeration on their electrocatalytic properties. Pt loading on model glassy carbon (GC) support is increased systematically from 1.8 to 10.6 μg Pt cm−2 and changes in the catalyst structure are followed by transmission electron microscopy. At low metal loadings (≤5.4 μg Pt cm−2) isolated single crystalline Pt nanoparticles are formed on the support surface by wet chemical deposition from H2PtCl4 precursor. An increase in the metal loading results, first, in a systematic increase of the average diameter of isolated Pt nanoparticles and, second, in coalescence of nanoparticles and formation of particle agglomerates. This behaviour is in line with the previous observations on carbon-supported noble metal fuel cell electrocatalysts. The catalytic activity of Pt/GC electrodes is tested in CO monolayer oxidation. In agreement with the previous studies (F. Maillard, M. Eikerling, O. V. Cherstiouk, S. Schreier, E. Savinova and U. Stimming, Faraday Discuss., 2004, 125, 357), we find that the reaction is strongly size sensitive, exhibiting an increase of the reaction overpotential as the particle size decreases below ca. 3 nm. At larger particle sizes the dependence levels off, the catalytic activity of particles with diameters above 3 nm approaching that of polycrystalline Pt. Meanwhile, Pt agglomerates show remarkably enhanced catalytic activity in comparison to either isolated Pt nanopraticles or polycrystalline Pt foil, catalysing CO monolayer oxidation at ca. 90 mV lower overpotential. Enhanced catalytic activity of Pt agglomerates is ascribed to high concentration of surface defects. CO stripping voltammograms from Pt/GC electrodes, comprising Pt agglomerates along with isolated single crystalline Pt nanoparticles from 2 to 6 nm size, feature double voltammetric peaks, the more negative corresponding to CO oxidation on Pt agglomerates, while the more positive to CO oxidation on isolated Pt nanoparticles. It is shown that CO stripping voltammetry provides a fingerprint of the particle size distribution and the extent of particle agglomeration in carbon-supported Pt catalysts.

370 citations

Journal ArticleDOI
TL;DR: The use of N,N-dimethylformamide (DMF) as both solvent and reductant in the solvothermal synthesis of Pt alloy nanoparticles (NPs), with a particular focus on Pt-Ni alloys, is reported on.
Abstract: Platinum alloy nanoparticles show great promise as electrocatalysts for the oxygen reduction reaction (ORR) in fuel cell cathodes. We report here on the use of N,N-dimethylformamide (DMF) as both solvent and reductant in the solvothermal synthesis of Pt alloy nanoparticles (NPs), with a particular focus on Pt–Ni alloys. Well-faceted alloy nanocrystals were generated with this method, including predominantly cubic and cuboctahedral nanocrystals of Pt3Ni, and octahedral and truncated octahedral nanocrystals of PtNi. X-ray diffraction (XRD) and high angle annular dark field scanning transmission electron microscopy (HAADF-STEM), coupled with energy dispersive spectroscopy (EDS), were used to characterize crystallite morphology and composition. ORR activities of the alloy nanoparticles were measured with a rotating disk electrode (RDE) technique. While some Pt3Ni alloy nanoparticle catalysts showed specific activities greater than 1000 μA/cm2Pt, alloy catalysts prepared with a nominal composition of PtNi disp...

370 citations

Journal ArticleDOI
TL;DR: In this paper, the authors used RRDE experiments to determine the values of the apparent number of electron transferred ( n ) and the percentage of peroxide (%H 2 O 2 ) released during the oxygen reduction reaction (ORR) in H 2 SO 4 at pH 1.9.

369 citations

Journal ArticleDOI
TL;DR: It is demonstrated that adding a small amount of gold to palladium and forming highly uniform nanoparticle cores make the platinum monolayer electrocatalyst significantly tolerant and very promising for the automotive application of fuel cells.
Abstract: Platinum is used as a cathode in fuel cells but undergoes dissolution during potential changes, hindering commercial application in electric vehicles. Sasaki et al. report a new class of stable electrocatalysts that consist of platinum monolayers on palladium–gold alloy nanoparticles.

369 citations

Journal ArticleDOI
TL;DR: A new approach is described to address, for the first time, both the activity and durability issues by using carbonsupported multiarmed starlike Pt nanowires (starlike PtNW/ C) as electrocatalysts as fuel cell cathode catalyst.
Abstract: Despite significant recent advances, the long-term durability of Pt catalyst at the cathode is still being recognized as one of the key challenges that must be addressed before the commercialization of proton exchange membrane fuel cells (PEMFCs). 2] The loss of Pt electrochemical surface area (ECSA) over time, because of corrosion of the carbon support and Pt dissolution/aggregation/Oswald ripening, is considered one of the major contributors to the degradation of fuel cell performance. Up to now, highly dispersed Pt nanoparticles (NPs, 2–5 nm) on carbon supports are still being widely used as the state-of-the-art commercial catalysts, and most reported studies are focused on nanoparticles of Pt. However, Pt with nanosized particle morphologies has high surface energies, thereby inducing severe Oswald ripening and/or grain growth during fuel cell operation. One-dimensional (1D) nanostructures of Pt, such as nanowires (NWs) and nanotubes (NTs), have been demonstrated to overcome the drawbacks of NPs in fuel cells, owning to their unique 1D morphologies. Yan et al. reported that unsupported Pt nanotubes exhibit much enhanced catalytic activity and durability as fuel cell cathode catalyst. Sun et al. and Zhou et al. reported the improved oxygen reduction reaction (ORR) activities of Pt NWs at the cathode under fuel cell operating conditions. However, up to now, the durability of Pt NW-based electrocatalysts has never been reported in the literature. Here we describe a new approach to address, for the first time, both the activity and durability issues by using carbonsupported multiarmed starlike Pt nanowires (starlike PtNW/ C) as electrocatalysts. Interestingly, the durability can be further improved by eliminating the carbon support, that is, using unsupported Pt nanowires as the cathode catalyst. As a result of their unique 1D morphology, the starlike Pt nanowire electrocatalyst can provide various advantages. First, the interconnected network consists of multiarmed, star-shaped 1D NWs with arm lengths of tens of nanometers which makes the Pt less vulnerable to dissolution, Ostwald ripening, and aggregation during fuel cell operation compared to Pt nanoparticles. Second, this network structure reduces the number of embedded electrocatalyst sites in the micropores of the carbon supports relative to those in nanogrannular Pt. Third, the mass transfer within the electrode can be effectively facilitated by networking the anisotropic morphology. Carbon-supported multiarmed starlike platinum nanowires were synthesized by the chemical reduction of a Pt precursor with formic acid in aqueous solution at room temperature and under ambient atmosphere. No surfactant, which is usually harmful for catalytic activities, was used in the experiments. Figure 1A and B show the representative scanning electron microscopy (SEM) and transmission electron microscopy (TEM) images, respectively, of carbon-supported Pt nanowires at 40 wt % loading of Pt. It can be seen that the assynthesized Pt is nanostar-shaped, being composed of several short arms of Pt nanowires. The number of arms of each nanostar is found to vary ranging from several to over ten. Occasionally, single-armed nanowires standing on the carbon surface can also be observed. Diameter and length of the arms of starlike Pt nanowires are about 4 nm and 15 nm, respectively. More interestingly, from the connected atomic arrangement shown in the high-resolution TEM (HRTEM) images (see Figure S1 in the Supporting Information and the inset in Figure 1B), the nanostar is found to be a single crystal. The fast Fourier transform (FFT; see inset in Figure S1) of the original HRTEM image shows a dotted pattern, further proving that the nanostar is a single crystal. This indicates that the formation mechanism of the nanostar involves seeded growth rather than an aggregation of seeded particles or an assembly process of the nanowires. The X-ray diffraction (XRD) pattern (Figure S2) confirms that the carbon-supported Pt nanowires are crystallized in a face-centered-cubic (fcc) structure similar to bulk Pt, which is consistent with the HRTEM investigations. We believe that the growth of the multiarmed starlike PtNWs on carbon black supports follows a similar process to that for Pt NWs on other supports. Typically, Pt nuclei are first formed in solution through the reduction of H2PtCl6 by HCOOH, and they deposit on the surface of carbon spheres. The freshly formed nuclei act as the sites for further nucleation through the continual absorption and reduction of Pt(IV) ions leading to the formation of particle seeds. For fcc structures, the sequence of surface energies is g{111} < g{100} [*] Dr. S. Sun, Dr. G. Zhang, Dr. D. Geng, Y. Chen, R. Li, Prof. X. Sun Department of Mechanical and Materials Engineering The University of Western Ontario London, Ontario N6A 5B9 (Canada) Fax: (+ 1)519-661-3020 E-mail: xsun@eng.uwo.ca

367 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
20231,041
20221,789
2021867
20201,180
20191,408
20181,449