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Preparation of a platinum electrocatalyst by coaxial pulse arc plasma deposition

View Article: PubMed Central - PubMed

ABSTRACT

We have developed a new method of preparing Pt electrocatalysts through a dry process. By coaxial pulse arc plasma deposition (CAPD), highly ionized metal plasma can be generated from a target rod without any discharged gases, and Pt nanoparticles can be deposited on a carbon support. The small-sized Pt nanoparticles are distributed over the entire carbon surface. From transmission electron microscopy (TEM), the average size of the deposited Pt nanoparticles is estimated to be 2.5 nm, and their size distribution is narrow. Our electrocatalyst shows considerably improved catalytic activity and stability toward methanol oxidation reaction (MOR) compared with commercially available Pt catalysts such as Pt black and Pt/carbon (PtC). Inspired by its very high efficiency toward MOR, we also measured the catalytic performance for oxygen reduction reaction (ORR). Our PtC catalyst shows a better performance with half-wave potential of 0.87 V, which is higher than those of commercially available Pt catalysts. The higher performance is also supported by a right-shifted onset potential. Our preparation is simple and could be applied to other metallic nanocrystals as a novel platform in catalysis, fuel cells and biosensors.

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(a) Cyclic voltammetric and (b), (c) amperometric curves for the MOR catalyzed PtC-CAPD, PtC-5%, PtC-20% and PtB in a 0.5 M H2SO4 solution containing 0.5 M methanol. (d) Pt_ECSA retention of each sample during the cycling treatments. The current densities (Y-axis) are normalized by the mass of Pt (mg). A scanning speed of 50 mV s−1 is used for the (a) cyclic voltammetric measurements, while constant potentials of 0.5 V and 0.4 V are used in the (b), (c) amperometric measurements.
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Figure 3: (a) Cyclic voltammetric and (b), (c) amperometric curves for the MOR catalyzed PtC-CAPD, PtC-5%, PtC-20% and PtB in a 0.5 M H2SO4 solution containing 0.5 M methanol. (d) Pt_ECSA retention of each sample during the cycling treatments. The current densities (Y-axis) are normalized by the mass of Pt (mg). A scanning speed of 50 mV s−1 is used for the (a) cyclic voltammetric measurements, while constant potentials of 0.5 V and 0.4 V are used in the (b), (c) amperometric measurements.

Mentions: The electrocatalytic activity of MOR was studied. The reaction for the entire MOR can be written as follows: CH3OH + H2O → CO2 + 6 H+ + 6e−. The first reaction step is written as CH3OH → COad + 4 H+ + 4e−. At the early stage, the methanol molecules are adsorbed to the Pt surface, and CO molecules are generated, which is described as COad. At the second step, water molecules are adsorbed to the Pt surface. The water molecules adjacent to COad are reactive to generate CO2 molecules (COad + OH− → CO2 + H+ + 2e−) [31–34]. For comparison, several commercially available Pt catalysts (PtB, PtC) with different Pt loading amounts (PtC-5% and PtC-20%) were also evaluated. Figure 3(a) shows the CV curves of the MOR catalyzed by different Pt catalysts. All the CV curves exhibit two noticeable anodic peaks, which are typical features of a MOR on a pure Pt surface [35–37]. In the case of our Pt catalyst and PtC-5%, an electric double-layer region is also observed within which the carbon support has a significant contribution. The area of the electric double-layer varies according to the surface area of the carbon supports. The current density of different Pt catalysts of the MOR is summarized in table 1. Our Pt catalyst shows higher current density than other commercially available catalysts.


Preparation of a platinum electrocatalyst by coaxial pulse arc plasma deposition
(a) Cyclic voltammetric and (b), (c) amperometric curves for the MOR catalyzed PtC-CAPD, PtC-5%, PtC-20% and PtB in a 0.5 M H2SO4 solution containing 0.5 M methanol. (d) Pt_ECSA retention of each sample during the cycling treatments. The current densities (Y-axis) are normalized by the mass of Pt (mg). A scanning speed of 50 mV s−1 is used for the (a) cyclic voltammetric measurements, while constant potentials of 0.5 V and 0.4 V are used in the (b), (c) amperometric measurements.
© Copyright Policy - open-access
Related In: Results  -  Collection

License 1 - License 2
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getmorefigures.php?uid=PMC5036468&req=5

Figure 3: (a) Cyclic voltammetric and (b), (c) amperometric curves for the MOR catalyzed PtC-CAPD, PtC-5%, PtC-20% and PtB in a 0.5 M H2SO4 solution containing 0.5 M methanol. (d) Pt_ECSA retention of each sample during the cycling treatments. The current densities (Y-axis) are normalized by the mass of Pt (mg). A scanning speed of 50 mV s−1 is used for the (a) cyclic voltammetric measurements, while constant potentials of 0.5 V and 0.4 V are used in the (b), (c) amperometric measurements.
Mentions: The electrocatalytic activity of MOR was studied. The reaction for the entire MOR can be written as follows: CH3OH + H2O → CO2 + 6 H+ + 6e−. The first reaction step is written as CH3OH → COad + 4 H+ + 4e−. At the early stage, the methanol molecules are adsorbed to the Pt surface, and CO molecules are generated, which is described as COad. At the second step, water molecules are adsorbed to the Pt surface. The water molecules adjacent to COad are reactive to generate CO2 molecules (COad + OH− → CO2 + H+ + 2e−) [31–34]. For comparison, several commercially available Pt catalysts (PtB, PtC) with different Pt loading amounts (PtC-5% and PtC-20%) were also evaluated. Figure 3(a) shows the CV curves of the MOR catalyzed by different Pt catalysts. All the CV curves exhibit two noticeable anodic peaks, which are typical features of a MOR on a pure Pt surface [35–37]. In the case of our Pt catalyst and PtC-5%, an electric double-layer region is also observed within which the carbon support has a significant contribution. The area of the electric double-layer varies according to the surface area of the carbon supports. The current density of different Pt catalysts of the MOR is summarized in table 1. Our Pt catalyst shows higher current density than other commercially available catalysts.

View Article: PubMed Central - PubMed

ABSTRACT

We have developed a new method of preparing Pt electrocatalysts through a dry process. By coaxial pulse arc plasma deposition (CAPD), highly ionized metal plasma can be generated from a target rod without any discharged gases, and Pt nanoparticles can be deposited on a carbon support. The small-sized Pt nanoparticles are distributed over the entire carbon surface. From transmission electron microscopy (TEM), the average size of the deposited Pt nanoparticles is estimated to be 2.5 nm, and their size distribution is narrow. Our electrocatalyst shows considerably improved catalytic activity and stability toward methanol oxidation reaction (MOR) compared with commercially available Pt catalysts such as Pt black and Pt/carbon (PtC). Inspired by its very high efficiency toward MOR, we also measured the catalytic performance for oxygen reduction reaction (ORR). Our PtC catalyst shows a better performance with half-wave potential of 0.87 V, which is higher than those of commercially available Pt catalysts. The higher performance is also supported by a right-shifted onset potential. Our preparation is simple and could be applied to other metallic nanocrystals as a novel platform in catalysis, fuel cells and biosensors.

No MeSH data available.


Related in: MedlinePlus