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|Ab-initio modeling of electrochemistry in proton-exchange-membrane fuel cells|
General - Engineering & Technology
|Summary||Instead of burning hydrocarbons, fuel cells are presented to be an alternative solution for the power generation problem by having the least amount of harmful effects. In current fuel cell models, chemical processes are coupled to transport and flow processes through simplified models, which neglect the details of real chemistry and thus fail to predict the correct trends of surface coverage in fuel cells.|
Multi-scale models for PEM fuel cells can be developed, in which not only transport and flow, but also the chemistry is simulated by the best available computational tools, here the Dynamic Monte Carlo (DMC)methodology. DMC simulations can predict the state of the catalyst surface quite accurately if they are provided by accurate rate constants for elementary reactions that are randomly chosen from a chemical mechanism based on their relative probabilities.
Ab-initio calculations have been used here to provide the necessary kinetic rate data for performing DMC simulations of oxygen reduction reaction (ORR) mechanism in PEM fuel cells. An efficient search algorithm is developed to locate the transition states of electron transfer reactions for large systems, for which such calculations were not feasible before. A set of consistent energetics are presented for the elementary electrochemical reactions in the ORR mechanism. Due to their prominent role, interaction of adsorbed O and OH on these reactions are investigated too. Using these data, the DMC results for the water discharge mechanism, the major subset of the ORR mechanism, is in very good agreement with experimental measurements.
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