Two types of solid oxide cells with different Ni-YSZ cermet microstructures have been aged in electrolysis and fuel cell modes for operating times ranging from 1000 to 15000 hours. The pristine and aged cermets have been reconstructed by synchrotron X-ray holotomography. Nickel agglomeration has been observed in the bulk of the operated samples inducing a significant loss of triple phase boundary lengths. The inspection of the microstructural properties has confirmed the stabilizing role of YSZ on Ni coarsening. Furthermore, the gradients of properties quantified at the electrolyte interface have revealed a depletion of Ni only in the electrochemically active region of the electrode. The process is strongly promoted for a coarse cermet microstructure when operated under electrolysis current. The evolution of the microstructural properties has been implemented in an in-house multiscale model. The simulations have shown that the loss of performance is dominated by the depletion of Ni in case of a coarse microstructure. Thanks to the computations, it has been shown that the Ni depletion is controlled by the cathodic overpotential. To explain this dependency, it has been proposed that the accumulation of oxygen vacancies in the double layer could deteriorate the Ni/YSZ interface and trigger the Ni depletion.
Diffusion barrier layers are typically
introduced in solid oxide fuel cells (SOFCs) to avoid reaction between
state-of-the-art cathode and electrolyte materials, La1–x
Sr
x
Co1–y
Fe
y
O3‑δ and yttria-stabilized zirconia (YSZ), respectively. However, commonly
used layers of gadolinia-doped ceria (CGO) introduce overpotentials
that significantly reduce the cell performance. This performance decrease
is mainly due to the low density achievable with traditional deposition
techniques, such as screen printing, at acceptable fabrication temperatures.
In this work, perfectly dense and reproducible barrier layers for
state-of-the-art cells (∼80 cm2) were implemented,
for the first time, using large-area pulsed laser deposition (LA-PLD).
In order to minimize cation interdiffusion, the low-temperature deposited
barrier layers were thermally stabilized in the range between 1100
and 1400 °C. Significant enhanced performance is reported for
cells stabilized at 1150 °C showing excellent power densities
of 1.25 W·cm–2 at 0.7 V and at a operation
temperature of 750 °C. Improved cells were finally included in
a stack and operated in realistic conditions for 4500 h revealing
low degradation rates (0.5%/1000 h) comparable to reference cells.
This approach opens new perspectives in manufacturing highly reproducible
and stable barrier layers for a new generation of SOFCs.
HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.
IDEAL-Cell is a new concept of a high temperature fuel cell operating in the range 600-700°C. It is based on the junction between the anode part of a PCFC and the cathode part of a SOFC through a mixed H+ and O2- conducting porous ceramic membrane. This concept, extensively described in the present paper, aims at avoiding all the severe pitfalls connected with the presence of water at the electrodes in both SOFC and PCFC concepts. Spark Plasma Sintering samples were designed specifically for proving the IDEAL-Cell concept. The first electrochemical results obtained at 600°C under hydrogen on millimeter thick samples show that IDEAL-Cell behaves like a high temperature fuel cell. It is estimated that the overall efficiency of this new concept should greatly surpass that of standard SOFCs and PCFCs and that the material constraints, especially in the case of interconnect materials, should significantly decrease
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.