High-Entropy Spinel Oxide as an On-Cell Reforming Layer for Carbon-Resistant Wet Methane SOFCs

Symmetric electrode (Ba 0.9 La 0.1 ) 0.97 Fe 0.95 Mn 0.05 O 3-δ (SE) enables simplified SOFC manufacturing with redox stability and better surface exchange kinetics under wet H 2 and ambient air. But under wet CH 4, SE suffers coking and phase instability. This study introduces a high-entropy spinel (CuLiFeCoNi) 1.4 Mn 1.6 O 4 (CL) as an on-cell reforming layer to protect the symmetric electrode and catalyze methane cracking. XRD, Raman, and XPS data obtained after wet CH 4 annealing reveal that CL maintains phase stability, lattice oxygen retention, and carbon resistance, unlike SE. Electrical conductivity relaxation yields superior CL methane kinetics ( k ex = 2.50 × 10 –3 cm s –1 at 750 °C). In YSZ-supported full cells with CL incorporated onto the SE anode, the peak power density triples to 73 mW cm –2 and boosts the OCV to 0.75 V under wet CH 4 . Bayesian Hilbert transform run DRT studies confirm that CL lowers the wet CH 4 reforming polarization losses with superior coking resistance.