Self-hydrating of a ceria-based catalyst enables efficient operation of solid oxide fuel cells on liquid fuels.

ABSTRACT

The commercialization of solid oxide fuel cells (SOFCs) that run on liquid hydrocarbon fuels is hindered by the poor coking tolerance of the state-of-the-art anode. Among the strategies developed, modulating the reforming reaction site's local steam/carbon ratios to enhance the coking tolerance is efficient but challenging. Here we report our rational design of a ceria-based catalyst (with a nominal composition of Ce0.95Ru0.05O2-δ, CR5O) that demonstrates remarkable tolerance to coking while maintaining excellent activity for direct utilization of liquid fuels in SOFCs. Under operating conditions, the catalyst is transformed to a partially reduced oxide frame covered with Ru nanoparticles (Ru/Ce0.95Ru0.05-xO2-δ, Ru/CR5-xO), as confirmed by experimental analyses. The Ru/CR5-xO demonstrates excellent self-hydration capability to remove the coke. When applied to the Ni-yttria-stabilized zirconia (Ni-YSZ) anode of an SOFC with liquid fuels, the catalyst enables excellent performance, achieving a peak power density of 1.010 W cm-2 without coking for ∼200 h operation (on methanol) at 750 °C. Furthermore, density functional theory calculations reveal that the high activity and coking tolerance of the Ru/CR5-xO catalyst-coated Ni-YSZ anode is attributed to the reduced energy barrier for the rate-limiting step and the formation of a COH intermediate for rapid carbon removal.