Transforming alumina into a fluorite framework through Cerium(IV) modulation: Toward developing superior ion conductors

Fluorite alumina exists as a mix of nano-fluorite crystals and amorphous regions challenging the long-standing understanding of alumina polymorphs. We introduce high-valence Ce(IV) as a structural modulator to incorporate oxygen into the alumina lattice, reducing vacancy concentration and restoring structural order by recovering amourphous regions, resulting in a novel fluorite alumina electrolyte as a successor in the fluorite electrolyte family following yttria-stabilized zirconia (YSZ) and doped ceria (Sm(III)/Gd(III)) systems. Notably, the Ce(IV)-modulated alumina fluorite electrolyte exhibits ionic conductivity exceeding 0.1 S cm⁻¹ and achieves fuel cell power output above 1000 mW cm⁻² at 500 °C. This excellent performance arise from a synergistic mechanism that boosts intrinsic O²⁻ mobility while promoting extrinsic proton conduction. Given alumina's natural abundance, low-cost and the remarkable properties achieved, our material offers an advanced electrolyte platform for next-generation low-temperature SOFCs and SOECs, leading the way for cost-effectiveness and accelerated commercialization for power and hydrogen production technologies.