Abstract
Molecular modelling is a novel approach in the
development of new catalyst materials. Method was used to
investigate Pt-based binary and ternary alloy catalysts
utilized in PEM (Proton Exchange Membrane) fuel cells.
The focus was on the development more effective cathode
materials, the functionality of which are understood also
on the molecular level. Further, the aim in the
development of new catalysts was to minimize the amount
of Pt needed and to reach high specific activity. In
order to compare the laboratory-made, commercial and new
non-synthesized Pt-based catalysts, the optimized crystal
and surface structures of catalysts were defined using
the molecular modelling techniques. The Pt structure was
modified by Cr, Co and Ir with an atomic ratio of 3:1,
2:1:1 and 1:1. The modelling results were used in order
to choose catalysts for experimental analyses. The
catalysts were prepared on carbon carrier by reduction of
metal salts. The catalyst content in the materials was 20
wt.%. In order to obtain required crystal structure, the
catalysts were heat-treated at temperatures 300 - 1000
°C. Transmission electron micrographs show that the
average particle size increases as a function of heat
treatment temperature. The stability of the alloy
catalysts was tested by electrochemical (voltammetric)
measurements by determining the border potential where
the modifier metals are starting to desorb from the
surface of the metal alloy. The experimental surface
analyses are consistent with the modelling results. After
the determination and comparison of structural and
electrostatic properties of catalysts, the oxygen
reduction mechanism was calculated on the Pt and Pt2CoCr
(001) surfaces. Based on the calculations, the reaction
occurs by a four-electron pathway, and the limiting
factor of the reaction is the dissociation of hydrogen
superoxide (HO2-) intermediate. The dissociation rate of
hydrogen superoxide can be supposed to have an effect on
the durability of membrane electrode assemblies (MEA).
The research indicated that the oxygen reduction reaction
can be controlled by optimizing the atomic structure of
Pt-based catalysts.
| Original language | English |
|---|---|
| Publication status | Published - 2006 |
| MoE publication type | Not Eligible |
| Event | Nordic PEMFC 06 - Stockholm, Sweden Duration: 25 Sept 2006 → 27 Sept 2006 |
Conference
| Conference | Nordic PEMFC 06 |
|---|---|
| Country/Territory | Sweden |
| City | Stockholm |
| Period | 25/09/06 → 27/09/06 |
