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Modelling of Porous Electrodes for an Optimized Material Design

This project is dedicated to a bottom-up approach to optimize the design of porous electrode materials devoted to biofuel cells and biosensors. These devices operate on the basis of complex enzymatic electrochemical redox reactions coupled to mass transfer of substrates (glucose and O2) and electron transfer within the pores of the structure and from/to the pore surfaces. The advantage of using porous materials for these devices lies in the very large internal surface area (where electron exchange takes place) to overall material volume ratio, yielding much larger current densities than on a simple solid bare electrode.

The global performance of the electrode is intimately related to the choice of the reagents and the placement within the pore structure but, above all, to the architecture of the material at the pore-scale. However, these materials have always been designed so far on an empirical basis regarding the thickness of the material and its pore size and organization. These parameters have a crucial impact on the competition between mass transport, enzymatic turn-over and heterogeneous electron transfer rate. A rational approach is hence really needed, based on a direct interplay between materials design and modelling to reach optimal performance.

The objective of the present project is four-fold. In a first step, careful models will be derived at the pore-scale. For tractable computational subsequent treatment, macroscale models will be obtained by upscaling their pore-scale analogues. Solutions of the pore-scale models, obtained from Direct Numerical Simulations on simple porous structures, will be compared to the solution of the corresponding up-scaled model as a validation step of the upscaling process. Validation of the overall modelling approach will be further performed by comparisons with experimental results using images of the real structure. In a second step, the electrode current-to-potential dependency with respect to the microstructure obtained by modelling will be exploited to optimize the porous architecture. In a third step, engineering of electrode prototypes, based on the resulting optimized materials, will be then carried out by conveniently tuning the pore structure. In the final part of the project, after a key step of enzymes (and electron mediator) immobilization within the porous structure to achieve a DET or MET operating mode, experiments on the synthetized electrodes will be performed using electroanalytical tests. This recursive and rational approach should lead to a real and decisive breakthrough in the efficiency improvement of the bio-devices to which these porous electrodes are dedicated.