Low Cost HEA Anode for Distributed Reforming and Prevention of Carbon Deposition in SOFC(18-RD-987)

Direct Internal Reforming Solid Oxide Fuel Cells require an anode material with good catalytic reforming and electrochemical reactivity. Although the current state-of-the-art solid oxide fuel cell anode consisting of nickel and yttrium-stabilized zirconia (Ni-YSZ) has excellent catalytic properties and stability for the H2 oxidation at the usual operation conditions, the use of Ni-YSZ anode with carbon containing fuels results in the deposition of large quantities of carbon on the nickel surface, resulting in a marked irreversible reduction of cell performance. Our approach is to replace Ni with a predominantly single phase multi-principal element alloy. Multi- principal element alloys (MPEAs) are a new alloy development strategy, where the base alloy has significant atom fractions of several elements. We propose to combine 3-5 elements to form a MPEA and make cermet with YSZ for the anode. In Phase I, we performed thermodynamic calculations to determine composition ranges for solid-solution alloys using 3-5 elements selected from their catalytic properties and potential for coking resistance. Selected alloys were fabricated and composited with YSZ to form MPEA-YSZ anode by both powder processing and magnetron sputtering methods. CH4-steam reforming tests showed that the reforming rate on MPEA-YSZ remains lower than on conventional Ni-YSZ as proposed during tests performed at 750°C. Carbon formation was not observed in post-test MPEA-YSZ by scanning electron microscopy - energy dispersive spectroscopy (SEM-EDS) and Raman spectroscopy. In Phase II, we will develop electrochemical and thermal models of the cell in its stack environment for selected MPEA compositions, which can provide the basis for tailoring the anode composition. Electrochemical testing and performance analysis will be done on button cells fabricated using the optimized composition of selected alloys and compared with the performance of the base line cell. Further testing will be performed with gas mixtures more representative of natural gas to avoid the need for a supplemental conventional pre-reformer.