Manufacturing methods of the electrolyte for Proton Conducting Cells

Protonic ceramic cells have attracted tremendous attention in the past decades due to their unique advantages, such as lower operating temperature and easier reversible operation. Moreover, in recent years, the hydrogen economy has been strongly favored by governmental and industrial bodies worldwide. To improve the development of proton conductor-based cells, rational design of high-performance electrolyte materials with novel compositions and proper manufacturing techniques are needed in order to scale-up the cells and make this technology ready for commercialization. In this work, the manufacturing methods of the electrolyte for protonic conducting solid oxide cells and their challenges are described, as part of a joint project of Politecnico Di Torino, Politecnico di Milano, University of California Irvine and SNAM, in the attempt to obtain low thickness electrolytes, along with the description of the imaging and analysis techniques employed. At first, a Yttria Stabilized Zirconia (YSZ) slurry is produced to better understand how its composition must be to obtain a suitable value of viscosity to perform tape casting, a scalable and industrially established manufacturing process, which has been completed for values of layer thickness of 400, 300, 200 and 100 μm. Consequently, trials of tape casting on a Ceria and Yttria doped Barium Zirconate (BZCY) slurry are reported, highlighting the need to obtain both a proper value of viscosity, which must be relatively low and checked performing rheology, while still keeping a quantity of binder that allows to peel off the dried slurry and, ultimately, perform sintering. Tape casting on the BZCY slurry has been successfully completed obtaining the following values of layer thickness: 400, 300, 200, 100, 20, 15, 10 and 5 μm. The BZCY slurry has been produced with the addition of a Manganese Oxide sintering aid, which has shown the capability to change the surface structure of BZCY using the scanning electron microscope (SEM). Also, various sintering protocols have been performed, proving that heating up the sample to 1350 °C, dwelling at the same temperature for two hours and cooling back to room temperature at a rate of 100 °C/h constitutes an effective strategy. It is expected that the technical readiness level of PCCs might advance more quickly, toward field demonstrations and commercialization for a clean and sustainable energy era.