Platinum nanoparticle - Wikipedia
T1 - Controllable ALD synthesis of platinum nanoparticles by tuning different synthesis parameters
Iron–platinum nanoparticle - Wikipedia
A is being developed for fuel cells that produces twelve times more catalytic activity than pure platinum. In order to achieve this performance, researchers anneal nanoparticles to form them into a crystalline lattice, reducing the spacing between platinum atoms on the surface and increasing their reactivity.
In another study, the growth of the palladium nuclei was found to be at the grain interior during electrodeposition on an AISI 316 grade stainless-steel electrode. It is well known that nucleation occurs preferentially at the holes or disorder state of the substrate on which the metal is to be deposited. Scanning electron micrographs of the surface of the stainless steel after electrodeposition of palladium nanoparticles at low and high magnifications are shown in Figures and , respectively. Although nucleation occurred preferentially at the grain boundaries, the extensive growth took place only for nuclei within the grain interior, as shown in . The probable reason for the discrepancy in deposition of palladium particles on the grain rather than on the grain boundary is the presence of oxide ridges at the grain boundaries where the formation of chromium oxide is easy at room temperature. Stainless steel consists of 18 wt.% chromium, which forms thin film oxides at room temperature. The oxidation process is more favorable at the grain boundaries because the formation of oxide nuclei at room temperature is energetically favorable due to the presence of defects. Although the formation of nuclei on such stainless-steel templates during electrodeposition of palladium was easy, subsequent growth of nuclei on top of the oxide ridge at the grain boundaries of the steel substrate was slow compared to that of the nuclei at the grain interior. The slow growth rate was attributed to the difficulty in the charge transfer due to the presence of highly resistive oxide film underneath the nuclei at the grain boundaries of the stainless-steel template.
Shape-directed platinum nanoparticle …
In order to study the role of electrode surface on electrodeposition, palladium nanoparticles were deposited on a freshly cleaved graphite surface. A microscopic investigation found that the palladium nanoparticles were faceted and their shape was mostly spherical, as shown in . The faceted characteristic of these particles is more clearly observed in the inset of . Nuclei formed at almost all parts of the electrode surface; however, the presence of a large number of nanoparticles near the edges and boundaries () indicates a preferential nucleation process.
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 ,-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 displayed activities close to 3000 μA/cm2Pt, or almost 15 times that of a state-of-the-art Pt/carbon catalyst. XRD and EDS confirmed the presence of two NP compositions in this catalyst. HAADF-STEM examination of the PtNi nanoparticle catalyst after RDE testing revealed the development of hollows in a number of the nanoparticles due to nickel dissolution. Continued voltage cycling caused further nickel dissolution and void formation, but significant activity remained even after 20 000 cycles.
Synthesis of Platinum Nanoparticles from K2PtCl4 …
presents the role of amorphous carbon substrate as a template for the electrodeposition of palladium nanoparticles. Although the template consists of carbon, the shape of the electrodeposited metallic particle differs from that of the cleaved graphite surface. In the case of the amorphous carbon substrate, the nuclei formed at random locations and fractal growth behavior was observed. In addition, the attachment between the deposits and carbon substrate was weak. All these results strongly indicate that the surface of the active template plays an important role in shape and size distribution of metallic nanoparticles during electrodeposition. presents the various active template substrates used for template-assisted electrodeposition of metallic nanostructures of mostly precious metals such as silver, gold, platinum, and palladium.
Palladium deposits with high specific surface areas, up to 50 mg, have been synthesized from palladium chloride solutions with additions of polyethylene glycol and polyvinyl pyrrolidone. Details of the globular structure of the deposits depend on the polymer additives. A comparison with electrochemically determined true surface areas demonstrates the rare coalescence of nanoparticles.
Green synthesis of platinum nanoparticles using Azadirachta indica ..
Full Text | Nanoparticle | Platinum
The challenge to control both the shape and composition of platinum nanoparticles ..
Synthesis of Porous Platinum Nanoparticles - Teng - …
the nanotubes appear to be porous and are capable of forming novel peptide – nanotube platinum– nanoparticle ..
microheaters with platinum nanoparticle catalyst ..
Catalytic hydrogen sensing using microheated platinum nanoparticle-loaded ..
MEBCS019 | Nanoparticle | Platinum
AB - Pt nanoparticles were successfully deposited using three different atomic layer deposition (ALD) methods, e.g. AB-type, ABC-type and static ABC-type ALD, on two different types of strontium titanate nanocuboids (STO-NCs) samples in a reaction temperature window of 125 °C-300 °C. The influence of reaction temperature, number of ALD cycles, type of substrate, 2nd reagent and type of ALD method on Pt nanoparticle deposition are comprehensively studied and discussed in this work. Varying the reaction temperature and number of cycles across the three different ALD methods affects Pt particle size, density, and loading. Surface termination of STO-NCs substrate will change deposited Pt nanoparticle growth orientation and thermodynamic shape. The B reagent besides platinum precursor can lead to different ligand decomposition mechanism when Pt precursors are exposed: oxygen allows more effective ligand combustion compared to water, however, the Pt particles are more oxidized according to XPS studies. We expect this work provides a way for tailoring nanoparticles with desired size, dispersion, exposed surfaces and chemical state etc, which helps controlling and optimizing their performance when applied as catalysts or nanosensors.
Shape-directed platinum nanoparticle synthesis: ..
The formation of nanostructures in active template-based synthesis results from growth of the nuclei that invariably nucleate at the holes and defects of the electrode substrate. Subsequent growth of these nuclei at the template yields the desired surface morphology of the nanostructures, which can therefore be synthesized by choosing the appropriate surface of the electrode. Highly oriented pyrolitic graphite (HOPG), for example, is used extensively as an electrode substrate for the electrodeposition of silver, gold, molybdenum, palladium, and platinum nanostructures. Electrodeposition initiates at the step edges, dislocations, and defect sites of the electrode surface. Vázquez et al. studied the early stages of overpotential deposition of silver on HOPG from silver-ion-containing acidic solution. It was shown that the initial deposition occurred at the step edges of the electrode surface, and silver nuclei were not found on the flat HOPG surface domains. The electrodeposition study of silver on the HOPG substrate using in-situ scanning tunneling microscopy revealed that at low over-potentials, the deposition process on the atomically flat terraces of HOPG was inhibited because of weak substrate-deposit interaction leading to preferential silver deposition at step edges and other surface defects. Such step-edge deposition involves the preferential nucleation and subsequent growth of nanoparticles on a certain crystal surface. shows a schematic diagram of step-edge synthesis. Favier et al. attempted to fabricate hydrogen sensors and switches with the help of palladium nanoparticles electrodeposited onto the graphite step edges. Stable, two dimensionally branched palladium islands, 100–160 nm in size, were electrodeposited on HOPG from an aqueous acidic palladium chloride solution with an excess of sodium perchlorate at a potential of a few millivolts above the threshold potential of the hydrogen evolution reaction. Platinum nanocrystals were deposited on the basal plane of HOPG from dilute (1.0 mM) PtCl - containing electrolytes using a pulsed potentiostatic method. The deposition of platinum nanocrystals occurred via an instantaneous nucleation and diffusion-limited growth mechanism which resulted in a narrow particle size distribution for mean crystallite diameters smaller than 40 Å.
Synthesis of nanosized platinum ..
N2 - Pt nanoparticles were successfully deposited using three different atomic layer deposition (ALD) methods, e.g. AB-type, ABC-type and static ABC-type ALD, on two different types of strontium titanate nanocuboids (STO-NCs) samples in a reaction temperature window of 125 °C-300 °C. The influence of reaction temperature, number of ALD cycles, type of substrate, 2nd reagent and type of ALD method on Pt nanoparticle deposition are comprehensively studied and discussed in this work. Varying the reaction temperature and number of cycles across the three different ALD methods affects Pt particle size, density, and loading. Surface termination of STO-NCs substrate will change deposited Pt nanoparticle growth orientation and thermodynamic shape. The B reagent besides platinum precursor can lead to different ligand decomposition mechanism when Pt precursors are exposed: oxygen allows more effective ligand combustion compared to water, however, the Pt particles are more oxidized according to XPS studies. We expect this work provides a way for tailoring nanoparticles with desired size, dispersion, exposed surfaces and chemical state etc, which helps controlling and optimizing their performance when applied as catalysts or nanosensors.
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