Proton-conducting ceramic fuel cells: Scale up and stack integration

We present our efforts to scale up proton-conducting ceramic fuel cells (PCFCs) from the button-cell level into small, multi-cell stacks. While recent advancements with lab-scale PCFCs are encouraging, there are few reports of scaling PCFC technology to the stack level. The compatibility of protonic-ceramic materials with stackpackaging materials - metallic interconnects, current collectors, glass-ceramic sealants, gaskets - has not been demonstrated. Here we show that through tuning of materials, fabrication procedures, and operating conditions, protonic-ceramic fuel cell stacks can achieve reasonable performance and low degradation. The MEA is based around barium cerate-zirconate perovskites. Better long-term stack durability is found with BaCe0.4Zr0.4Y0.1Yb0.1O3-delta (BCZYYb) electrolyte. The anode support is a nickel-electrolyte composite, while the cathode is BaCo0.4Fe0.4Zr0.1Y0.1O3-delta (BCFZY). Planar MEAs reach 5 cm(2) in active area, and are packaged within ferritic-steel interconnects and macor frames to form multi-cell stacks. Our three-cell stack demonstrates encouraging performance, reaching 0.69 and 0.47 W cm(-2) under H-2 and CH4 fuels, respectively, at 600 degrees C. A gadolinium-doped ceria cathode-electrolyte interlayer reduces degradation rates to 1.5% kh(-1) at 0.1 A cm(-2) and 3.3% kh(-1) at 0.4 A cm(-2) at 550 degrees C. No chromium transport is observed. Degradation mechanisms and the role of the GDC interlayer are postulated.

Automated summary

This study demonstrates the scaling up of proton-conducting ceramic fuel cells (PCFCs) into small, multi-cell stacks with reasonable performance and low degradation through material tuning, fabrication procedures, and operating condition adjustments. Specific materials such as the BCZYYb electrolyte and the BCFZY cathode, as well as packaging with ferritic-steel interconnects and macor frames, contribute to the long-term durability and performance of the fuel cell stacks.