"WORK PERFORMED
The following main activities have been performed during the project:
- validation of a physically-based continuum electrochemical model with tomographic and electrochemical impedance spectroscopy (EIS) data of Ni:ScSZ (scandia stabilized zirconia) anodes (both conventional and scaffold electrodes) prepared and tested in previous projects;
- fabrication of more than 10 symmetric SOFC anodes: scaffolds of ScSZ, prepared with custom ink, sintered on YSZ (yttria stabilized zirconia) electrolyte disk, infiltrated up to 19 times with Ni(NO3)2 (nickel nitrate) solution, fired and reduced;
- degradation experiments by annealing selected samples at constant temperature for up to 200h while monitoring electrochemical impedance in real time;
- 3D tomographic reconstruction (focused ion beam-SEM) of selected fresh and degraded anodes, image segmentation and advanced quantification of the microstructural properties;
- interpretation of the electrochemical degradation data according to the validated physically-based model and the 3D tomographic results, with quantification of the fractal roughness and the microstructural degradation mechanisms occurring at different length scales.
Additional activities complemented the research, such as:
- application of the same methodology described above to redox-cycled electrodes;
- development of open-source software (TauFactor) to quantify relevant microstructural properties from tomographic datasets;
- guidelines for the rational design of 3D manufactured and conventional electrodes by using a model-guided approach;
- multi-length scale X-ray tomography and characterisation of diffusion in porous electrodes.
MAIN RESULTS
The main result of the project is the development of an integrated experimental/modelling framework which allowed for the fundamental understanding of the electrochemical phenomena in SOFC electrodes and, more specifically, of the degradation processes affecting nickel nanoparticles. In particular, the project proved that the rapid electrochemical degradation of infiltrated SOFC anodes stems from the evolution of interfaces at the nanoscale, beyond the resolution currently achieved by tomographic techniques, thus solving a long-standing dilemma regarding nanostructured and redox-cycled electrodes. As an immediate consequence, the research results suggest that nickel wetting properties are key to stop the degradation while practices currently adopted by the community, such as sintering inhibitors, are ineffective. Additional guidelines for structured SOFC electrodes were also published.
DISSEMINATION
The list of papers authored/co-authored by the Fellow during the project is reported in the ""Publication"" page. They include 9 papers in peer-reviewer international scientific journals (plus 2 currently under review and 4 in preparation), 1 contribution in a book chapter, 4 contributions in conference proceedings, the participation to 7 national and international conferences delivering oral presentations, the dissemination of results in 2 seminars and in 2 workshops."
