COMP 231 |
| Compared to surface science experiments under UHV conditions, electrochemical systems (such as fuel cells) combine a whole variety of additional effects. These range from the nanostructure of the highly disperse catalyst particles over the presence of the electrolyte and the multi-component environment to the reaction conditions of finite temperature, pressure, and electrode potential. Due to this complexity our knowledge about the ongoing processes is mostly limited to the macroscopic regime. However, nowadays theoretical methods are able to provide a deeper insight into structures and processes at the atomistic level, which together with experiments could lead to a better understanding. Within this talk I will first present theoretical studies on the oxygen reduction reaction (ORR) occurring at the cathode of PEM-fuel cells. Starting with the gas-phase system effects from the reactive surrounding as well as environmental parameters are successively included, finally providing a more realistic description. In order to describe the electrochemical interfaces developing in these systems we formulated the extended {\it ab initio} atomistic thermodynamics method, which allows calculating (p,T,Φ)-phase diagrams of electrode/eletrolyte-interfaces from first principles. It turned out that the model of a pure and perfect catalyst surface, which is often used to study this reaction, is clearly incomplete. Instead, structure and composition of the catalyst are significantly modified. Afterwards, calculations on alternative catalyst materials (Pt-based alloys and nano-structured Ir) that experimentally show enhanced reaction rates are discussed. We find that the electrode potential is also an important parameter for actively tuning electrode morphologies and nanostructuring. |
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Bold Predictions in Theoretical Chemistry: A Symposium in Honor of One of the Boldest, Bill Goddard, on the Occasion of his 70th Birthday
2:00 PM-5:10 PM, Tuesday, August 21, 2007 BCEC -- 160B, Oral
Division of Computers in Chemistry |