Naslov
A Comparison of Electrocatalytic Properties and Electrochemical Stability of Deposited Platinium-Based Catalysts for DMFC

Autori
Horvat, Roberta ; Metikoš-Huković, Mirjana ; Gusić, Zrinka

Vrsta, podvrsta i kategorija rada
Sažeci sa skupova, sažetak, znanstveni

Izvornik
Summaries 9, 4th European Symposium on Electrochemical Engineering / I. Novosad - : Czech Society of Chemical Engineering (CSCHE), 1996

Skup
12th International Congress of Chemical and Process Engineering (CHISA’96)

Mjesto i datum
Prag, Češka Republika, 25.08.1996. - 30.08.1996

Vrsta sudjelovanja
Poster

Vrsta recenzije
Nije recenziran

Ključne riječi
fuel-cell; electrocatalysis; underpotential deposition; adsorption; bifunctional catalysts; platinum; ruthenium; tin; methanol; bifunctional mechanism

Sažetak
Direct methanol fuel cell (DMFC) is one of the most serious candidates for application in electric vehicles. Among several problems connected with the practical use of DMFC, the most important is to find an adequate catalyst whose performances would make the application of DMFC commercial. It is a well known fact that in acid methanolic media, Pt is the best choice when reaction rate is considered. But, methanol oxidation under these conditions is incomplete, and reaction intermediates accumulate on the electrode surface in the course of time. Consequently, the active Pt sites are blocked and current density decreases. The most promising catalysts for the direct methanol oxidation are platinum modified electrodes (bimetallic catalysts). In this study, bimetallic Pt_70-Ru_30 and Pt-Sn electrodes were investigated. Pt_70-Ru_30 electrodes were produced by the potential-controlled-deposition (PCD) from a solution containing Pt and Ru ions in stoichiometric ratio 70:30. Pt-Sn electrodes were prepared by the underpotential deposition (UPD) of tin from a solution containing 5x10^-4 M SnSO_4 at the Pt electrode surface. The Sn surface coverage was evaluated according to the method proposed by Lamy-Pitara et. al.[1]. Measurements were performed by EG&G PAR Potentiostat/Galvanostat Model 273 with a Lock-in Amplifier Model 5301 controlled by IBM PC 30 computer. The kinetics of the methanol oxidation reaction was studied in 1 M HClO_4 solution using cyclic voltammetry (CV), linear polarization (LP) and chronoamperometry (CA). The effect of the solution hydrodynamics was studied using RDE. The following kinetic parameters were evaluated for Pt, Pt_70-Ru_30 and Pt-Sn catalysts: Tafel slopes, diffusion coefficients, reaction rate constants and reaction orders. The adsorptive behaviour of methanol on the Pt electrode surface followed a Flory-Huggins isotherm (DELTA G=-12ą1 kJmol^-1) and on the Pt_70-Ru_30 surface a Langmuir isotherm (DELTA G=-29ą2 kJmol^-1). Our results showed that Pt-Ru catalysts were stable under experimental conditions and exhibited higher activity for methanol oxidation reaction than pure Pt (Fig.1). Pt-Sn catalysts of any surface composition did not show enhanced activity towards electrooxidation reaction and were relatively stable in acid media.

Izvorni jezik
Engleski

Znanstvena područja
Kemija

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