Porous/dense bilayer BaZr_0.8Y_0.2O_3-δ electrolyte matrix fabricated by tape casting combined with solid-state reactive sintering for protonic ceramic fuel cells

Perovskite-type yttrium-doped barium zirconate (BZY) has been considered as attractive electrolyte material for protonic ceramic fuel cells (PCFCs) due to its high bulk proton conductivity, excellent chemical stability and mechanical robustness. However, it requires very hash sintering conditions to obtain a dense ceramic, which will be unfavourable to the fabrication of anode-supported PCFCs. In this study, new cell structure based on porous/dense bilayer BaZr_0.8Y_0.2O_3-δ (BZY) electrolyte matrix was designed for PCFCs, facilitating the densification of electrolyte thin film and the nanostructured anode preparation by impregnation. The matrix was fabricated by bilayer co-tape casting combined with solid-state reactive sintering from the starting powders of BaCO₃, ZrO₂ and Y₂O₃ as well as NiO as sintering aid and graphite as pore former. The effects of graphite content on the microstructure of porous electrolyte layer (PEL) and the fuel cell performance were investigated. When the graphite content was 40 g in 165 g starting powders, the obtained PEL had the highest porosity and suitable shrinkage rate. With 20 wt% impregnated NiO anode, the single cell based on porous/dense bilayer BZY electrolyte matrix with 40 g graphite in 165 g PEL starting powders achieved the best performance with a maximum power density of 184 mW cm⁻² at 650 °C and operated with a stable output voltage of 0.72 V for 20 h at a constant current density of 100 mA cm⁻² during H₂/ambient air operation. The results indicate that the design and fabrication of porous/dense bilayer BZY electrolyte matrix is promising for the development of cost-effective PCFCs.