Dispersion Of Pt Nanoparticles Research Articles

Chelating agent assisted microwave synthesis of carbon supported Pt nanoparticles for low temperature polymer electrolyte fuel cells

Colloidal suspensions of almost spherical crystalline Pt nanoparticles with a narrow size distribution were synthesized using a microwave synthesis process. Pt ( phen ) 2 2 + complex (phen = 1,10-phenanthroline, C 12H 10N 2) was used as a precursor which was incorporated onto commercial Vulcan XC-72 carbon powder. X-ray diffraction and transmission electron microscopy were used to characterize the Pt/C catalysts. It was found that the Pt nanoparticles were uniform in size and highly dispersed on the carbon black supports. The chelating agent improves the Pt particle size as well as the dispersion of Pt nanoparticles. In the PEMFC experiments, the current density and power density of the catalysts were as high as those of the reference commercial catalysts.

Excellent dispersion and electrocatalytic properties of Pt nanoparticles supported on novel porous anatase TiO2 nanorods

We synthesize, for the first time, a new Pt based catalyst for direct methanol fuel cells using homemade novel porous anatase TiO2 nanorods as a new catalyst support. Pt nanoparticles are prepared by an improved ethylene glycol reduction method and supported on the surface of TiO2 with excellent dispersion and without any aggregates. The structure and elemental composition of the TiO2 and Pt/TiO2 catalyst are characterized by transmission electron micrography (TEM), nitrogen sorption, energy-dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD). The electrocatalytic properties of the Pt/TiO2 catalyst for methanol and carbon monoxide electro-oxidation reactions are investigated by cyclic voltammetry (CV) in an acidic medium. Apparent electrocatalytic activity for methanol electro-oxidation reaction, high carbon monoxide tolerance and good stability are all observed for the Pt/TiO2 catalyst. These may be attributed to the excellent dispersion of the Pt nanoparticles and the special properties of the TiO2 support. These results imply that this Pt/TiO2 catalyst has promising potential applications in direct methanol fuel cells.

Fabrication and Characterization of Pt/C−TiO2Nanotube Arrays as Anode Materials for Methanol Electrocatalytic Oxidation

A carbon-modified TiO2 nanotube (C−TiO2 NT) array is fabricated by depositing carbon in TiO2 NTs, which are prepared by anodization of the Ti sheet. Well-dispersed Pt nanoparticles (NPs) are electrochemically deposited on the C−TiO2 NTs. The performances of the as-prepared NT array electrode in the methanol oxidation reaction (MOR) as an anode are investigated. The results present in this study highlight such a finding: depositing partly graphitized carbon on the inside of TiO2 NTs can significantly enhance the catalytic efficiency. An optimum forward oxidation peak current density (Ipf) of 71.6 mA cm−2 is obtained from the Pt/C−TiO2 NT anode at a low Pt loading of 23 μg cm−2. The achieved Ipf is almost 27 times that achieved on Pt-modified TiO2 NTs without carbon modification. The enhanced catalytic efficiency is mainly attributed to the superior electrical conductivity of the deposited carbon, which facilitates the well dispersion of Pt NPs, charge transfer during the MOR, and removal of the byproduct C...

Controlled synthesis of mesoporous carbon modified by tungsten carbides as an improved electrocatalyst support for the oxygen reduction reaction

Mesoporous carbon was modified with tungsten carbides by the carbothermal hydrogen reduction of a layer of chemisorbed 1:12 phosphotungstic anions (PW12O403−) on carbon surfaces. Depending on the temperature of carbothermal treatment, different tungsten species, i.e., W, W2C, WC, were formed on the carbon matrix. No significant changes in both surface areas and mesostructures were observed during the formation of various tungsten species on carbon surfaces under high-temperature conditions. A uniform dispersion of Pt nanoparticles (1–6 nm) can be achieved via nanoconfinement on the surfaces of both mesoporous carbon and tungsten carbide-modified mesoporous carbon. Pt nanoparticles supported on mesoporous carbons modified with tungsten carbide (Pt/WC-C) exhibit enhanced electrocatalytic activities relative to the control, in which mesoporous carbons without carbide modification were directly used as a support (Pt/C). In addition, both enhanced thermal stability and good electrochemical stability were observed for the Pt/WC-C electrocatalyst.

Electrocatalytically Active Graphene-Platinum Nanocomposites. Role of 2-D Carbon Support in PEM Fuel Cells

The use of a 2-D carbon nanostructure, graphene, as a support material for the dispersion of Pt nanoparticles provides new ways to develop advanced electrocatalyst materials for fuel cells. Platinum nanoparticles are deposited onto graphene sheets by means of borohydride reduction of H2PtCl6 in a graphene oxide (GO) suspension. The partially reduced GO-Pt catalyst is deposited as films onto glassy carbon and carbon Toray paper by drop cast or electrophoretic deposition methods. Nearly 80% enhancement in the electrochemically active surface area (ECSA) can be achieved by exposing partially reduced GO-Pt films with hydrazine followed by heat treatment (300 °C, 8 h). The electrocatalyst performance as evaluated from the hydrogen fuel cell demonstrates the role of graphene as an effective support material in the development of an electrocatalyst.

Development of composite anode electrocatalyst for direct methanol fuel cells

Different effects of support hydrophilicity and metal-oxide on the performance of Pt-based catalysts were investigated with the aim of improving the mass activities toward methanol electrooxidation. Both potentiodynamic and potentiostatic measurements revealed that improved surface hydrophilicity of multi-wall carbon nanotubes (MWCNTs) could promote the dispersion of Pt nanoparticles and, consequently, promote the Pt utilization and reduce the polarization in methanol electrooxidation. In addition, WO3 was shown to play a supportive role in enhancing catalytic activity. The interaction between Pt and WO3 was examined by CO-stripping and CO oxidation transient experiments. The results suggested that the activity and the kinetics of monolayer COads electrooxidation of Pt nanoparticles are enhanced by the adjacent WO3 via a bifunctional mechanism, which accounts for improved activity in methanol electrooxidation.

Photocatalytic Activities of Graphitic Carbon Nitride Powder for Water Reduction and Oxidation under Visible Light

Graphitic carbon nitride (g-C3N4) with a band gap of 2.7 eV is studied as a nonmetallic photocatalyst for H2 or O2 evolution from water under ultraviolet (UV) and visible light. The g-C3N4 catalyst exhibits activities for water reduction into H2 or water oxidation into O2 in the presence of a proper sacrificial electron donor or acceptor, respectively, even without the need for precious metal cocatalysts. When bis(1,5-cyclooctadiene)platinum complex [Pt(cod)2] (a nonionic complex) is used as a precursor of Pt cocatalyst instead of H2PtCl6 (an ionic complex), enhanced H2 evolution activity is acquired. This difference in activity is primarily due to the better dispersion of Pt nanoparticles on g-C3N4, which is considered to originate from the better access of Pt(cod)2 to the g-C3N4 surface, as compared to that of H2PtCl6 in the preparation process. Unmodified g-C3N4 produces O2 from an aqueous silver nitrate solution upon UV irradiation (λ > 300 nm), although N2 release due to self-decomposition of g-C3N4 ...

Highly dispersed platinum nanoparticles on carbon nanocoils and their electrocatalytic performance for fuel cell reactions

Highly graphitic carbon nanocoils (GCNC) were synthesized through the catalytic graphitization of carbon microspheres obtained by the hydrothermal carbonization of different saccharides (sucrose, glucose and starch) and were used as a support for Pt nanoparticles. The Pt nanoparticles were deposited by means of a polymer mediated-polyol method. The Pt catalysts were characterized both physically (XRD, TEM, HRTEM and XPS) and electrochemically (electrooxidation of methanol in an acid medium). The electrocatalysts thus prepared show a high dispersion of Pt nanoparticles, with diameters in the 3.0–3.3 nm range and a very narrow particle size distribution. These catalytic systems possess high electroactive Pt surface areas (up to 85 m 2 g −1 Pt) and they exhibit large catalytic activities towards methanol electrooxidation (up to 201 A g −1 Pt). Moreover, they have a high resistance against oxidation, which is considerably greater than that of the Pt/Vulcan system.

Highly dispersed platinum supported on nitrogen-containing ordered mesoporous carbon for methanol electrochemical oxidation

Nitrogen-containing ordered mesoporous carbons (NOMCs) characteristic of CMK-3 were nanocasted from mesoporous silica SBA-15 using aniline as carbon precursor. The influence of synthesis condition on the structural parameters of NOMCs were systematically investigated using N 2 adsorption, powder X-ray diffraction (XRD), transmission electron microscopy, X-ray photoelectron spectroscopy (XPS), elemental analysis and thermogravimetric analysis (TGA). The 2D hexagonally ordered nitrogen-containing mesoporous carbon could be synthesized in a wide temperature range (600–950 °C), with Brunauer–Emmett–Teller (BET) surface area varying from 988 to 1166 m 2/g and pore size tunable from 2.7 to 3.3 nm. The N/C molar ratio in the framework of mesoporous carbon was found to be highly dependent on the synthesis condition and reduced from 9.5% to 4.8% as the synthesis temperature increased from 600 to 950 °C. XPS showed that nitrogen atoms were incorporated in graphitic sheets as quaternary nitrogen and pyridine-like nitrogen. The ca. 0.6 eV lower binding energy of Pt nanoparticles in contrast to that of bulk Pt indicated a strong interaction between nitrogen atoms and Pt nanoparticles, which was critical to the uniform dispersion of Pt nanoparticles on the nitrogen-containing mesoporous carbon. The CO stripping peak potentials depended on both the N/C ratio as well as Pt particles size. The activities of methanol oxidation on Pt/NOMCs were investigated by cyclic voltammograms and electrochemical impedance spectroscopy (EIS). The Pt/NOMCs showed generally high CO tolerance and comparable activity to Pt/XC-72 under the identical condition.

γ-Ray irradiation as highly efficient approach for synthesis of supported high Pt loading cathode catalyst for application in direct methanol fuel cell

In this study, a γ-ray irradiation approach without addition of any commonly used reducing chemicals has been explored to synthesize carbon-supported high Pt loading (i.e., 80 wt.%) cathode catalyst for direct methanol fuel cell. Compared with the Pt catalyst prepared by impregnation-NaBH 4 reduction approach, the supported Pt catalyst synthesized by γ-ray irradiation has better dispersion of Pt nanoparticles on the carbon support with smaller particle size and narrower size distribution and has demonstrated enhanced catalytic activity toward oxygen reduction reaction and improved fuel cell performance.

Effect of PVP on the Dispersity of Pt Nanoparticles and Catalytic Activity in Synthesis of Pt/C Catalysts for Fuel Cell

Pt-loaded carbon black for the catalyst of a PEM fuel cell was synthesized with different molar ratios of polyvinylpyrrolidone and <TEX>$H_2PtCl_6$</TEX> solution to improve the dispersion of Pt nanoparticles on carbon black and decrease the size of Pt nanoparticles. From transmission electron microscopy results, Pt nanoparticles of a size of approximately 2 nm were highly dispersed when the polyvinylpyrrolidone concentration was 10mM. The electrochemical activity of the synthesized Pt/C catalysts was investigated by cyclic voltammetry, showing that the as-synthesized Pt-loaded carbon black catalyst had the best activity at a polyvinylpyrrolidone concentration of 10 mM.

Platinum–carbon nanotube interaction

The interaction between evaporated Pt and pristine or oxygen-plasma-treated multiwall carbon nanotubes (CNTs) is investigated. Pt is found to nucleate at defect sites, whether initially present or introduced by oxygen plasma treatment. The plasma treatment induces a uniform dispersion of Pt nanoparticles at the CNT surface. The absence of additional features in the C 1 s core level spectrum indicates that no mixed Pt–C phase is formed. The formation of C–O–Pt bonds at the cluster-CNT interface is suggested to reduce the electronic interaction between Pt nanoparticles and the CNT surface.

Ordered silicon nanocones as a highly efficient platinum catalyst support for direct methanol fuel cells

Platinum nanoparticles were electrodeposited on ordered silicon nanocones (SNCs) and used as the catalyst for methanol electro-oxidation in direct methanol fuel cells (DMFCs). Because of uniform dispersion of Pt nanoparticles and the high surface area, the Pt-SNC electrode exhibited superior electrocatalytic properties toward the methanol electro-oxidation, with the onset potential of 0.08 V (vs. SCE). According to chronoamperometric analysis and CO stripping cyclic voltammetric (CV) study, the Pt/SNC electrode had a stable electro-oxidation activity with a very good CO tolerance. The Si surface oxide surrounding the Pt nanoparticles on the SNCs was suggested to play a key role in improving the CO tolerance via the bifunctional mechanism.

Influence of Hierarchical Porosity in Carbon Material on Electrocatalytic Property of Supported Pt Nanoparticles

The influence of hierarchical porosity on electrocatalytic property was investigated with Pt nanoparticles supported on three types of carbon materials, namely, commercial Vulcan XC-72, ordered mesoporous carbon CMK-5, and hierarchical carbon aerogel (HCA). The electrocatalytic activity of carbon supported Pt nanoparticles was verified by cyclic voltammetry in H 2SO 4 and CH 3OH solution. Pt/HCA presented superior performance with higher peak current (7.5 mA·cm −2) and electrochemical active area (128.0 m 2·g −1). This could be attributed to the carbon aerogel with continuous but nonperiodical mesopore structure, which facilitated dispersion of Pt nanoparticles and mass transport around reactants and products.

Hydrogen adsorption properties of single-walled carbon nanotube—Nanocrystalline platinum composites

Single-walled carbon nanotubes (SWNTs) have been synthesized by the pyrolysis of methane using hydrogen decrepitated Mischmetal (Mm) based AB 3 alloy hydride catalyst by catalytic chemical vapour deposition (CCVD) technique. The use of metal hydrides as catalysts for the bulk synthesis of good quality SWNTs by CCVD technique has been demonstrated. Nanocrystalline Pt dispersed single-walled carbon nanotubes (Pt/SWNT) have been prepared by chemical reduction method using functionalized SWNT. SWNTs and Pt/SWNTs have been characterized by SEM, TEM, HRTEM, Raman, TGA and XRD studies. Hydrogen storage properties of as-grown, purified SWNT and nanocrystalline Pt dispersed SWNT have been investigated using high-pressure Seiverts’ apparatus in the pressure range 1–100 bar and at 298 and 125 K. The effects of purification and dispersion of Pt nanoparticles on the hydrogen storage capacity have been discussed based on the chemisorption process.

Ordered mesoporous carbon decorated with rare earth oxide as electrocatalyst support for Pt nanoparticles

Ordered mesoporous carbon with large porosity was surface-modified with PrO x and subsequently deposited with Pt nanoparticles by microwave heating. Transmission electron microscopy images indicated that PrO x could improve the dispersion of Pt nanoparticles. The electrocatalytic activity of Pt catalysts was evaluated according to hydrogen adsorption region of cyclic voltammograms and electrochemical impedance spectroscopy. Pt/C–PrO x exhibited excellent performance in H 2SO 4, with a larger electrochemical active area and lower charge-transfer resistance than that of Pt/C. It is mainly due to enhanced dispersion of Pt nanoparticles and improved hydrogen adsorption on support.

Preparation of High Performance Pt/CNT Catalysts Stabilized by Ethylenediaminetetraacetic Acid Disodium Salt

AbstractA novel method with ethylenediaminetetraacetic acid disodium salt (EDTA‐2Na) as a stabilizing agent was developed to prepare highly dispersed Pt nanoparticles on carbon nanotubes (CNTs) to use as proton exchange membrane (PEM) fuel cell catalysts. These nanocatalysts were obtained by altering the molar ratio of ethylenediaminetetraacetic acid disodium salt to chloroplatinic acid (EDTA‐2Na/Pt) from 1:2, 1:1, 2:1 to 3:1. The well‐dispersed Pt nanoparticles of around 1.5 nm in size on CNTs were obtained when the EDTA‐2Na/Pt ratio was maintained at 1:1. And the Pt/CNT catalyst exhibited large electrochemical active surface areas, very high electrocatalytic activity and excellent stability in the oxidation of methanol at room temperature. The Pt/XC‐72R catalyst with narrow size distribution was also prepared by this method for comparison purposes. Comparison of the catalytic properties of these catalysts revealed that the activity of the Pt/CNT catalyst was a factor of ∼3 times higher than that of the Johnson Matthey catalyst and ∼2 times higher than that of our Pt/XC‐72R catalyst, which can be assigned to the high level of dispersion of Pt nanoparticles and the particular properties of the CNT supports.

Platinum nanoparticles supported on activated carbon fiber as catalyst for methanol oxidation

Activated carbon fiber (ACF) with high specific surface area has been used as support in the preparation of Pt nanoparticles electrocatalyst (Pt/ACF) for direct alcohol fuel cells. It is found that the Pt nanoparticles on ACF are highly and homogeneously dispersed with a narrow size distribution in the range of 1.5–3.5 nm with an average size of 2.4 nm. In comparison with the commercial E-TEK Pt/C catalyst, the Pt/ACF catalyst exhibits much higher catalytic activity for methanol, ethanol and isopropanol oxidation, which are about 2.4 times as high as that of the former. The Pt/ACF catalyst is observed to be significantly more stable during the constant current density polarization and continuous cyclic voltammetry in comparison with Pt/C catalyst. Both the uniform dispersion of Pt nanoparticles and strong interactions between Pt nanoparticles and ACF are of benefit to achieve the performance improvement of Pt/ACF catalyst.

Nb-TiO 2 supported Pt cathode catalyst for polymer electrolyte membrane fuel cells

The Nb-doped TiO 2 nanostructure (Nb-TiO 2) was prepared as a support of metal catalyst in polymer electrolyte membrane fuel cells. Using the Nb-TiO 2 nanostructure support, we prepared the Nb-TiO 2 supported catalyst. The Nb-TiO 2 supported Pt catalyst (Pt/Nb-TiO 2) showed the well dispersion of Pt catalysts (∼3 nm) on the Nb-TiO 2 nanostructure supports (∼10 nm). The Pt/Nb-TiO 2 showed an excellent catalytic activity for oxygen reduction compared with carbon supported Pt cathode catalyst. The enhanced catalytic activity of Pt/Nb-TiO 2 in electrochemical half cell measurement may be mainly due to well dispersion of Pt nanoparticles on Nb-TiO 2 nanosized supports. In addition, from XANES spectra of Pt L edge obtained with the supported catalysts, the improved catalytic activity of Pt/Nb-TiO 2 for oxygen reduction may be caused by an interaction between oxide support and metal catalyst.

Hydrogen storage properties of nanocrystalline Pt dispersed multi-walled carbon nanotubes

MWNTs have been synthesized by the pyrolysis of acetylene using hydrogen decrepitated Mischmetal (Mm)-based AB 3 alloy hydride catalyst using chemical vapor deposition (CCVD) technique. Nanocrystalline Pt dispersed multi-walled carbon nanotubes (Pt/MWNTs) have been prepared by chemical reduction method using functionalized MWNT. MWNT and Pt/MWNT have been characterized by SEM, TEM, HRTEM, Raman, TGA and XRD studies. Hydrogen storage properties of as-grown, purified and nanocrystalline Pt dispersed MWNT have been investigated using high-pressure Seiverts’ apparatus in the pressure range of 1–100 bar and at 298 and 125 K. The effects of purification and dispersion of Pt nanoparticles on the hydrogen storage capacity have been discussed.