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ID: 240066.1, MPI für Dynamik komplexer technischer Systeme / Physical and Chemical Process Engineering
Pt/Ru Colloidal Catalysis : Characterisation and Determination of Kinetics for Methanol Electrooxidation
Authors:Vidakovic, T.; Christov, M.; Sundmacher, K.; Nagabhushana, K.; Fei, W.; Kinge, S.; Bönnemann, H.
Language:English
Title of Proceedings:3rd Gerischer Symposium - Electrocatalysis : Theory and Experiment
Start Page:38
Name of Conference/Meeting:3rd Gerischer Symposium - Electrocatalysis : Theory and Experiment
Place of Conference/Meeting:Berlin, Germany
(Start) Date of Conference/Meeting
 (YYYY-MM-DD):
2005-07-06
End Date of Conference/Meeting 
 (YYYY-MM-DD):
2005-07-08
Review Status:not specified
Audience:Experts Only
Abstract / Description:In this study the electrochemical oxidation of methanol was studied on three different PtRu carbon supported catalysts on a membrane electrode assembly (MEA) in a cyclone flow cell [1]. The catalysts were synthesised by a salt-reduction colloidal method using different metal salt precursors and reducing agents [2]. The catalysts were characterised by non-electrochemical (EDX, XRD and TEM) and electrochemical (cyclic voltammetry in base electrolyte and CO stripping) methods. Their activities towards methanol oxidation were tested in steady state experiments at 22 and 60oC. The obtained experimental data were fitted into a model for methanol oxidation [3]. The model includes methanol adsorption on the Pt-sites and formation of a C-adsorbate, OHads formation on the Ru sites and surface reaction between C-adsorbate and OHads. The determined kinetic parameters were used to explain a difference in the catalysts activity and were correlated to catalysts morphology. For the experiments, MEAs were prepared by spraying the catalyst onto a Nafion® membrane followed by hot pressing to the back diffusion layer. The metal loading was 1 mg cm-2 and the nominal bulk composition was Pt:Ru 50:50. All catalysts were 30 wt % PtRu supported on Vulcan XC-72. In the working electrode compartment a 1M solution of methanol in water was circulated at flow rate of 10 l h-1. The supporting electrolyte in the counter electrode compartment was 1 M sulphuric acid. The real surface area was determined by CO stripping. The overall Pt:Ru composition of 50:50 was confirmed by EDX analysis for all catalysts. In XRD analysis only the peak reflections of the platinum f.c.c. structure were seen. Lattice constants for the two catalysts were close to the lattice constant of pure Pt or Pt-reach alloy, while lattice constant of the third catalyst was close to lattice constant of PtRu alloy of almost nominal composition (50:50). TEM analysis revealed a uniform particle size distribution and dispersion over the support. Particle size determined by TEM analysis was lower than by XRD analysis. CO stripping surface area was estimated to be more than one half of XRD surface area. In steady state experiments E – log(I) correlation gave two characteristic potential regions. The slope of this correlation in a linear region was different for different electrocatalysts and temperature dependent as well (≈120 – 140 mV dec-1 at 22oC and about 110 mV dec-1 at 60oC). According to presented model observed slope is not a result of a single rate determining step in a reaction mechanism, but is rather due to a mutual influence of two reaction steps (here methanol adsorption and surface reaction between adsorbed species). References [1] T. Vidaković, M. Christov, K. Sundmacher, Electrochimica Acta, 49(2004)2179. [2] (a) H. Bönnemann, R. M. Richards, Eur. J. Inorg. Chem. (2001)2455 (b) H. Bönnemann, S. Kinge, in preparation. [3] T. Vidaković, M. Christov, K. Sundmacher, J. Electroanal. Chem. submitted.
External Publication Status:published
Document Type:Conference-Paper
Communicated by:Kai Sundmacher
Affiliations:MPI für Dynamik komplexer technischer Systeme/Physical and Chemical Process Engineering
External Affiliations:University of Chemical Technology and Metallurgy
Department of Physical Chemistry
1756 Sofia, Bulgaria
Faculty of Technology and Metallurgy
Department of Physical Chemistry and Electrochemistry
Karnegijeva 4
11120 Belgrade, Serbia and Montenegro
Max-Planck-Institut für Kohlenforschung
Kaiser-Wilhelm-Platz
45470 Mühlheim an der Ruhr
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