Within composite electrodes for solid oxide fuel cells (SOFCs), electrochemical reactions take place at the so-called three-phase boundary (TPB), which is the contact perimeter where the electron-conducting phase, the ion-conducting phase and the porous phase meet. Such a TPB is conventionally regarded as a mono-dimensional line and efforts have been made to increase its length per unit of electrode volume in order to reduce the activation losses. In this study, by using physically-based modelling, 3D tomography and impedance spectroscopy, we show that the electrochemical reactions take place within an extended region around the geometrical TPB line. Such an extended region is in the order of 4 nm in Ni-ScSZ anodes [1] while approaches hundreds of nanometres in LSM-YSZ cathodes [2]. These findings have significant implications for preventing the degradation of nanostructured anodes, which is due to the coarsening of the fractal roughness of Ni nanoparticles [1], as well as for the optimisation of composite cathodes, indicating that the adsorption and surface diffusion of oxygen limit the rate of the oxygen reduction reaction (ORR) [2]. In both anodes and cathodes, the results point out that the surface properties of the materials are key in determining the performance and lifetime of SOFCs, demonstrating the benefits of adopting a model-based approach in the study of fuel cell electrodes. References [1] A. Bertei, E. Ruiz-Trejo, K. Kareh, V. Yufit, X. Wang, F. Tariq, N.P. Brandon, Nano Energy 38 (2017) 526. [2] A. Bertei, M.P. Carpanese, D. Clematis, A. Barbucci, M.Z. Bazant, C. Nicolella, Solid State Ionics 303 (2017) 181.

Physically-based modelling of solid oxide fuel cells: overcoming the three-phase boundary paradigm

A. Bertei
Investigation
;
C. Nicolella
Supervision
;
2017-01-01

Abstract

Within composite electrodes for solid oxide fuel cells (SOFCs), electrochemical reactions take place at the so-called three-phase boundary (TPB), which is the contact perimeter where the electron-conducting phase, the ion-conducting phase and the porous phase meet. Such a TPB is conventionally regarded as a mono-dimensional line and efforts have been made to increase its length per unit of electrode volume in order to reduce the activation losses. In this study, by using physically-based modelling, 3D tomography and impedance spectroscopy, we show that the electrochemical reactions take place within an extended region around the geometrical TPB line. Such an extended region is in the order of 4 nm in Ni-ScSZ anodes [1] while approaches hundreds of nanometres in LSM-YSZ cathodes [2]. These findings have significant implications for preventing the degradation of nanostructured anodes, which is due to the coarsening of the fractal roughness of Ni nanoparticles [1], as well as for the optimisation of composite cathodes, indicating that the adsorption and surface diffusion of oxygen limit the rate of the oxygen reduction reaction (ORR) [2]. In both anodes and cathodes, the results point out that the surface properties of the materials are key in determining the performance and lifetime of SOFCs, demonstrating the benefits of adopting a model-based approach in the study of fuel cell electrodes. References [1] A. Bertei, E. Ruiz-Trejo, K. Kareh, V. Yufit, X. Wang, F. Tariq, N.P. Brandon, Nano Energy 38 (2017) 526. [2] A. Bertei, M.P. Carpanese, D. Clematis, A. Barbucci, M.Z. Bazant, C. Nicolella, Solid State Ionics 303 (2017) 181.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11568/879383
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