Studies on state and structure of noble metals in electrocatalyst made by coprecipitation method

The electrocatalysts of Pt/C, PtRu/C and Ru/C were prepared by the impregnation method. The facet characterization, the dispersion and the particle size for the catalysts were determined by means of X-ray diffraction and transmission electron microscopy. X-ray photoelectron spectroscopy was also used to analyze the state and the valency of the noble metals. The results show that the particle size was in nanometer range and the binary metals have come into being an alloy. The platinum in the catalysts existed in zero valency. The valency of the ruthenium on the surface is different from that in the body, while the ruthenium on the surface existed in oxide-form. PtRu/C and Pt/C are of good activity to the electrooxidation of hydrogen except Ru/C. PtRu/C is more tolerant of CO than Pt/C, and CO is only adsorbed on Pt.

Carbon-supported Pd–Ir catalyst as anodic catalyst in direct formic acid fuel cell

It was reported for the first time that the electrocatalytic activity of the Carbon-supported Pd-Ir (Pd-Ir/C) catalyst with the suitable atomic ratio of Pd and Ir for the oxidation of formic acid in the direct formic acid fuel cell (DFAFC) is better than that of the Carbon-supported Pd (Pd/C) catalyst, although Ir has no electrocatalytic activity for the oxidation of formic acid. The potential of the anodic peak of formic acid at the Pd-Ir/C catalyst electrode with the atomic ratio of Pd and Ir = 5:1 is 50 mV more negative than that and the peak current density is 13% higher than that at the Pd/C catalyst electrode.

Highly ordered mesoporous carbons as electrode material for the construction of electrochemical dehydrogenase- and oxidase-based biosensors

In this work, the excel lent catalytic activity of highly ordered mesoporous carbons (OMCs) to the electrooxidation of nicotinamide adenine dinucleotide (NADH) and hydrogen peroxide (H2O2) was described for the construction of electrochemical alcohol dehydrogenase (ADH) and glucose oxidase (GOD)-based biosensors.

Platinum-coated gold nanoporous film surface: Electrodeposition and enhanced electrocatalytic activity for methanol oxidation

This report describes the preparation of Pt-nanoparticle-coated gold-nanoporous film (PGNF) on a gold substrate via a simple "green" approach. The gold electrode that has been anodized under a high potential of 5 V is reduced by freshly prepared ascorbic acid (AA) solution to obtain gold nanoporous film electrode. Then the Pt nanoparticle is grown on the electrode by cyclic voltammetry (CV).

The mechanism of formic acid electro oxidation on iron tetrasulfophthalocyanine-modified platinum electrode

The mechanism of formic acid electrooxidation on iron tetrasulfophthalocyanine (FeTSPc) modified Pt electrode was investigated with electrochemical methods. It was found that a "third-body" effect of FeTSPc on Pt electrode predominates during the electrooxidation process based on unusual electrochemical results. The modification leads formic acid electrooxidation to take place through a desired direct pathway, in which the mechanism is proposed to be the gradual dehydrogenation of formic acid and the reaction of formate with hydroxyl species.

Preparation of Pd/C catalyst for formic acid oxidation using a novel colloid method

A novel colloid method using (WO3)(n)center dot xH(2)O as colloidal source was developed to prepare Pd/C catalyst for formic acid oxidation. Transmission electron microscopy image shows that the Pd/C nanoparticles have an average size of 3.3 nm and a narrow size distribution. Electrochemical measurements indicate that the Pd/C catalyst exhibits significantly high electrochemical active surface area and high catalytic activity with good stability for formic acid oxidation compared with that prepared by common method.

Highly active PtRu catalysts supported on carbon nanotubes prepared by modified impregnation method for methanol electro-oxidation

A simple and rapid synthesis method (denoted as modified impregnation method, MI) for PtRu/CNTs (MI) and PtRu/C (MI) was presented. PtRu/CNTs (MI) and PtRu/C (MI) catalysts were characterized by transmission electron microscopy (TEM) and X-ray diffractometry. It was shown that Pt-Ru particles with small average size (2.7 nm) were uniformly dispersed on carbon supports (carbon nanotubes and carbon black) and displayed the characteristic diffraction peaks of Pt face-centered cubic structure.

Hydrogen Vanadate as an Effective Stabilizer of Pd Nanocatalysts for Formic Acid Electroxidation

In this paper, a simple chemical reduction route is discussed that results in small size, uniform dispersion of Pd nanoparticles supported on carbon black. HVO42-, the tridentate oxoanion with its O-O distance of 2.76 angstrom, closely matching with the Pd-Pd distance (2.75 angstrom), is expected to be an effective stabilizer for Pd according to the lattice size-matching binding model (Finke, R. G.; Ozkar, S. Coord. Chem. Rev. 2004, 248, 135). Because it has never been tested, HVO42- is exploited and found to be a very simple and effective stabilizer.

Highly efficient electrocatalytic oxidation of formic acid by electrospun carbon nanofiber-supported PtxAu100-x bimetallic electrocatalyst

Electrospun carbon nanofiber-supported bimetallic PtxAu100-x electrocatalysts (PtxAu100-x/CNF) were prepared by electrochemical codeposition method. The composition of PtAu bimetallic nanoparticles could be controlled by varying the ratio of H2PtCl6 and HAuCl4. Scanning electron microscopy images showed that bimetallic nanoparticles had coarse surface morphology with high electrochemically active surface areas. X-ray diffraction analysis testified the formation of PtAu alloys. PtxAu100-x/CNF electrocatalysts exhibited improved electrocatalytic activities towards formic acid oxidation by providing the selectivity of the reaction via dehydrogenation pathway and suppressing the formation/adsorption of poisoning CO intermediate, indicating that PtxAu100-x/CNF is promising electrocatalyst in direct formic acid fuel cells.

High activity PtRu/C catalysts synthesized by a modified impregnation method for methanol electro-oxidation

A modified impregnation method was used to prepare highly dispersive carbon-supported PtRu catalyst (PtRu/C). Two modifications to the conventional impregnation method were performed: one was to precipitate the precursors ((NH4)(2)PtCl6 and Ru(OH)(3)) on the carbon support before metal reduction: the other was to add a buffer into the synthetic solution to stabilize the pH. The prepared catalyst showed a much higher activity for methanol electro-oxidation than a catalyst prepared by the conventional impregnation method. even higher than that of current commercially available, state-of-the-art catalysts. The morphology of the prepared catalyst was characterized using TEM and XRD measurements to determine particle sizes, alloying degree, and lattice parameters. Electrochemical methods were also used to ascertain the electrochemical active surface area and the specific activity of the catalyst.

Kinetic study of formic acid oxidation on carbon supported Pd electrocatalyst

The oxidation of formic acid at the Pd/C catalyst electrode is a completely irreversible kinetic process with the reaction order of 1.0. The oxidation rate of formic acid is increased with increasing the concentration of formic acid and is decreased with increasing H+ concentration. The apparent negative reaction order with respect to H+ is about -0.18 or -0.04 in H2SO4 or HClO4 solution respectively, because bisulfate anions would inhibit formic acid oxidation at some extent. The kinetic parameters, charge transfer coefficient and the diffusion coefficient of formic acid were obtained under the quasi steady-state conditions.

Facile synthesis of PtRu/C electrocatalyst with high activity and high loading for passive direct methanol fuel cell by synergetic effect of ultrasonic radiation and mechanical stirring

The PtRu/C electrocatalyst with high loading (PtRu of 60 wt%) was prepared by synergetic effect of ultrasonic radiation and mechanical stirring. Physicochemical characterizations show that the size of PtRu particles of as-prepared PtRu/C catalyst is only several nanometers (2-4 nm), and the PtRu nanoparticles were homogeneously dispersed on carbon surface. Electrochemistry and single passive direct methanol fuel cell (DMFC) tests indicate that the as-prepared PtRu/C electrocatalyst possessed larger electrochemical active surface (EAS) area and enhanced electrocatalytic activity for methanol oxidation reaction (MOR). The enhancement could be attributed to the synergetic effect of ultrasound radiation and mechanical stirring, which can avoid excess concentration of partial solution and provide a uniform environment for the nucleation and growth of metal particles simultaneously hindering the agglomeration of PtRu particles on carbon surface.

Nanoelectrocatalyst based on high-density Au/Pt hybrid nanoparticles supported on a silica nanosphere

A high-efficiency nanoelectrocatalyst based on high-density Au/Pt hybrid nanoparticles supported on a silica nanosphere (Au-Pt/SiO2) has been prepared by a facile wet chemical method. Scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy are employed to characterize the obtained Au-Pt/SiO2. It was found that each hybrid nanosphere is composed of high-density small Au/Pt hybrid nanoparticles with rough surfaces. These small Au/Pt hybrid nanoparticles interconnect and form a porous nanostructure, which provides highly accessible activity sites, as required for high electrocatalytic activity. We suggest that the particular morphology of the AuPt/SiO2 may be the reason for the high catalytic activity. Thus, this hybrid nanomaterial may find a potential application in fuel cells.

Controllable synthesis of pd nanocatalysts for direct formic acid fuel cell (DFAFC) application: From pd hollow nanospheres to pd nanoparticles

The controllable synthesis of nanosized carbon-supported Pd catalysts through a surface replacement reaction (SRR) method is reported in this paper. Depending on the synthesis conditions the Pd can be formed on Co nanoparticles surface in hollow nanospheres or nanoparticles structures. Citrate anion acts as a stabilizer for the nanostructures, and protonation of the third carboxyl anion and hence the nanostructure and size of the resulting catalysts are controlled via the pH of the synthesis solution. Pd hollow nanospheres, containing smaller Pd nanoparticles, supported on carbon are formed under the condition of pH 9 reaction solution. Meanwhile, highly dispersed carbon-supported Pd nanoparticles can be formed with higher pH (pH >= 10). All catalysts prepared through the SRR method show enhanced activities for the HCOOH electro-oxidation reaction compared to catalysts reduced by NaBH4.