Interface-reinforcing sintering step for highly stable operation of proton-conducting fuel cell stack

Proton conducting fuel cells (PCFCs) are promising power generation systems due to their low operating temperature by conducting proton activated with low kinetic energy. However, well-known proton conducting materials such as Y-doped BaCeO3−δ (BCY), Y-doped BaZrO3−δ (BZY), and BaCe0.8-xZrxY0.1Yb0.1O3−δ (BCZYYb) have a limitation in that the planar cell is fragile during operation attributed to the low mechanical strength. This study proposes a two-step sintering method to fabricate mechanically superior PCFC large cells based on the BCZYYb electrolyte. The two-step sintering process consists of a heat treatment step at a temperature in which the anode and electrolyte have similar shrinkage values during the sintering process and another step that can improve the bonding strength of each layer by grain growth. The vulnerable anode/electrolyte interface, which acts as a significant mechanical failure factor, is optimized through the two-step sintering process. Two-step sintered cells show high mechanical stability in lab-scale and 6 cm × 6 cm planar cells for stack systems. A two-step sintered large cell exhibits outstanding stability during 350 h at 600 °C with the stack system. Our strategy provides a method to build practical proton-conducting fuel cells.