Screen Printed Porous La0.20Sr0.25Ca0.45TiO3 Fuel Electrode Scaffold Microstructures: Optimisation of Interaction with Impregnated Catalysts for More Durable Performance

Solid Oxide Fuel Cells (SOFC) offer an efficient method of electricity and heat production through electrochemical conversion of hydrocarbon fuels (e.g. methane) rather than direct combustion in conventional boiler units. The current industrial standard SOFC anode material is the Ni-based cermet. Although it shows high electrocatalytic activity for H₂ and CO oxidation, it suffers from redox instability, Ni-grain agglomeration, gas feed sulfur intolerance and severe coking in the presence of hydrocarbon fuels. This deactivates the catalyst over time, hence a suitable replacement anode material is highly desired. La_0.20Sr_0.25Ca_0.45TiO₃ (LSCT_A-) is a promising candidate for this role, acting as a ‘backbone’ structure into which electrocatalytic particles (NiO and CeO₂) may be impregnated. This material has previously been used as an anode material in short-stack and full-scale testing at Hexis AG. Short-stack (5 cells) tests showed initial good performance (running at 200 mA cm^-2) at 900 °C, however degradation was observed between 50 – 100 hours of operation. ¹ Whilst in 1kW (nominal) Hexis Galileo 1000 N micro combined heat and power unit tests, an initial power output of ~700 W was obtained, decreasing to 250 W after 600 hours. ¹ Post-test analysis revealed that non-optimal anode backbone microstructures and a small layer thickness led to poor current distribution and the generation of localised temperature ‘hotspots’ within the cells, leading to degradation of stack performance over time ¹ (despite the initial comparability to the Ni-CGO standard at Hexis). Current research is focussing on the optimisation of the interaction between the backbone microstructure and impregnated electrocatalytic particles in order to improve electrochemical performance whilst minimising degradation. This paper will discuss initial research into optimisation of screen printed anode structures and the interaction with impregnated particles, including: NiO, CuO, CeO₂ and lanthanum strontium chromium manganite (LSCrM).

Reference:

1.           Verbraeken, M. C. et al. Short stack and full system test using a ceramic A-site deficient strontium titanate anode in 11th European SOFC and SOE Forum, 1–13, (2014).