Leveraging Ni Ex-SolvedPerovskite Structure to Designa Ternary-Phase-Catalyzed Composite Anode for High-Performance DirectAmmonia Solid Oxide Fuel Cells

Ammonia is considered a revolutionary hydrogen vector, presenting an exceptional energy density with a high hydrogen content. Herein, an advanced ternary-phase composite (TPC) anode with high catalytic activity and enhanced durability for application to direct ammonia solid oxide fuel cells (DA-SOFCs) is reported. When exposed to fuel, a TPC anode material consisting of NiO, YSZ, and A-site-deficient La_0.4Sr_0.4Ti_0.9Ni_0.1O_3‑δ (LSTN) is adorned with an in situ exsolution of Ni nanoparticles ranging in size from ∼15 to 20 nm on the surface of LSTN perovskite. The TPC anode decorated with ex-solved Ni nanoparticles showed improved reaction kinetics for ammonia decomposition with outstanding electrochemical performance compared to a cell with a conventional Ni-YSZ cermet anode. The SOFC with a 10LSTN-Ni-YSZ TPC anode demonstrated maximum power densities of 1.466 and 1.354 W·cm^–2 at 700 °C, when fueled with H₂ and NH₃, respectively. This represented performance increments of 24 and 30% compared to that of the conventional Ni-YSZ anode-supported SOFC. The TPC anode cell revealed stable operation with a slight variation in the voltage from 0.936 to 0.934 V for ∼100 h, whereas the conventional cell showed severe degradation under operation with NH₃. These improvements in power generation and durability were attributed to the abundance of active sites induced by ex-solved Ni nanoparticles on the surface of LSTN responsible for promoting NH₃ cracking and subsequent H₂ electro-oxidation. This study provides a facile approach to exploiting in situ exsolution to tailor the anode surface for direct ammonia SOFC applications.