Slightly ruthenium doping enables better alloy nanoparticle exsolution of perovskite anode for high-performance direct-ammonia solid oxide fuel cells

Fuel flexibility is one of the most distinguished advantages of solid oxide fuel cells (SOFCs) over other low-temperature fuel cells. Furthermore, the combination of ammonia fuel and SOFCs technology should be a promising clean energy system after considering the high energy density, easy transportation/storage, matured synthesis technology and carbon-free nature of NH₃ as well as high efficiency of SOFCs. However, the large-scale applications of direct-ammonia SOFCs (DA-SOFCs) are strongly limited by the inferior anti-sintering capability and catalytic activity for ammonia decomposition reaction of conventional nickel-based cermet anode. Herein, a slightly ruthenium (Ru) doping in perovskite oxides is proposed to promote the alloy nanoparticle exsolution, enabling better DA-SOFCs with enhanced power outputs and operational stability. After treating Ru-doped Pr_0.6Sr_0.4Co_0.2Fe_0.75Ru_0.05O_3-δ single-phase perovskite in a reducing atmosphere, in addition to the formation of two layered Ruddlesden-Popper perovskites and Pr₂O₃ nanoparticles (the same as the Ru-free counterpart, Pr_0.6Sr_0.4Co_0.2Fe_0.8O_3-δ), the exsolution of CoFeRu-based alloy nanoparticles is remarkably promoted. Such reduced Pr_0.6Sr_0.4Co_0.2Fe_0.75Ru_0.05O_3-δ composite anode shows superior catalytic activity and stability for NH₃ decomposition reaction as well as anti-sintering capability in DA-SOFCs to those of reduced Pr_0.6Sr_0.4Co_0.2Fe_0.8O_3-δ due to the facilitated nanoparticle exsolution and stronger nanoparticle/substrate interaction. This work provides a facile and effective strategy to design highly active and durable anodes for DA-SOFCs, promoting large-scale applications of this technology.