Leveraging Ni Ex-Solved Perovskite Structure to Design a Ternary-Phase-Catalyzed Composite Anode for High-Performance Direct Ammonia 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 La0.4Sr0.4Ti0.9Ni0.1O3-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.