Fundamental materials engineering of robust solid oxide electrolysis cells for terrestrial and space applications.

Abstract

In this work, a brief summary of the benefits of integrating Rh/Ce1-xGdxO2-δ (CGO)-impregnated LSCTA- fuel electrode active layers into commercial standard solid oxide electrolysis cells (SOECs) is provided, before presenting results pertaining to the optimisation of air electrode layers and high-conductivity perovskite electrode current collection layers, which better match the performance and stability of this novel fuel electrode. Firstly, results from solid-oxide electrochemical oxygen pump testing confirmed that 'traditional' (La0.80Sr0.20)0.95MnO3 (LSM)- and La0.60Sr0.40CoO3 (LSC)-based air electrodes exhibit rapid degradation during oxygen evolution. Replacement with Pr6O11-impregnated CGO layers, employing LSM and La0.95Ni0.60Fe0.40O3 (LNF) as current collectors, significantly improved the durability and oxygen pumping capability of these membranes (for use in a wide variety of applications on Earth and in space). Secondly, alternative fuel electrode current collectors (to Ni(O) layers) were investigated through synthesis, characterisation and electrical testing of a series of La0.90Mn0.95X0.05O3 compositions (where X = Ni, Fe, Cu or Ti). The La0.90Mn0.95Ti0.05O3 (LMTA-) composition showed the highest stability of 'effective' electrical conductivity in N2 (p(O2) ∼10-5 atm) and 5% H2/95% N2 (p(O2) = 10-18-10-19 atm) and was deemed suitable for testing as a fuel-side current collector in SOEC mode. Finally, durability test data for SOECs utilising these optimised air and fuel-side material sets, using a pure carbon dioxide fuel gas, will highlight the system-scale benefits of addressing stability through engineering of electrode materials at nanoscales, for energy conversion technology applications on Earth and in space.

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