Ru–Ni co-exsolution from B-site excessive proton-conducting perovskite for durable anode catalytic layers in direct ammonia PCFCs

Direct ammonia protonic ceramic fuel cells (DAPCFCs) offer a promising pathway for efficient power generation, owing to the high energy density, ease of storage, and enhanced safety of ammonia compared to hydrogen. However, their practical application is limited by poor durability, particularly at intermediate temperatures below 600 °C. To address this challenge, we design a Ru and Ni co-doped B-site-excessive proton-conducting perovskite BaZr 0.1 Ce 0.7 Y 0.1 Yb 0.1 Ru 0.02 Ni 0.05 O 3-δ (R2N5), as a robust anode catalyst layer (ACL) material for DAPCFCs. Under high-temperature reducing conditions, Ru and Ni are reduced and exsolved from the perovskite lattice to form nanoparticles separately, effectively catalyzing ammonia decomposition at intermediate temperatures. When incorporated into a single PCFC cell operating under ammonia fuel, the cell with ACL shows a 34% enhancement in the power output at 550 °C compared to the reference cell. The cell also exhibited excellent durability, with 8% voltage degradation over 350 h of continuous operation in ammonia, compared to 18.2% degradation within 100 h for the reference cell. Post-test analysis revealed that the R2N5 ACL mitigated Ni coarsening and agglomeration in the anode, contributing to the improved performance and lifetime of the DAPCFC. This work demonstrates a rational strategy to overcome the durability bottleneck of DAPCFCs by engineering multifunctional, exsolution-enabled ACLs.