Performance degradation in proton-conducting ceramic fuel cell and electrolyzer stacks

Abstract

Proton-conducting ceramics are emerging as enabling materials for efficient electrochemical electricity generation, energy storage, and fuels synthesis. In this work, we present longer-term degradation results for protonic-ceramic fuel cells and electrolyzers based on a BaCe0.4Zr0.4Y0.1Yb0.1O3−δ (BCZYYb) electrolyte. The cells are packaged within unit-cell stacks, including metallic interconnects, current collectors, sealing glasses and gaskets. Durability is found to be superior in protonic-ceramic electrolyzers in comparison to fuel cells. Operating conditions have a large impact on degradation rates; better stability is found at fuel-cell operating temperatures above 600 °C, and electrolyzer steam feeds below 20 %. We find that both fuel-cell and electrolyzer degradation is greatly reduced via the introduction of a gadolinium-doped ceria interlayer between the electrolyte and the air–steam electrode. Fuel-cell degradation falls to 1.2% khr−1 under methane fuel at 600 °C; electrolyzer degradation is reduced to 1% khr−1 at 550 °C and 50% steam. Further analyses of electrochemical impedance spectroscopy and distribution of relaxation times provide insight to root processes and degradation phenomena in protonic electroceramics.