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

Abstract

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 stack-packaging 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−δ (BCZYYb) electrolyte. The anode support is a nickel-electrolyte composite, while the cathode is BaCo0.4Fe0.4Zr0.1Y0.1O3−δ (BCFZY). Planar MEAs reach 5 cm2 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 H2 and CH4 fuels, respectively, at 600 ∘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 ∘C. No chromium transport is observed. Degradation mechanisms and the role of the GDC interlayer are postulated.