In-situ assembled cobalt-free PSFNRu nanocomposites as bi-functional electrodes for direct ammonia symmetric solid oxide fuel cells

Symmetric solid oxide fuel cells (SSOFCs) have gained significant attention owing to their cost-effective fabrication, superior thermomechanical compatibility, and enhanced long-term stability. Ammonia (NH₃), an excellent hydrogen carrier, is a promising clean energy source with high energy density, easy transportation and storage. Notably, NH₃ contained only nitrogen and hydrogen, making it carbon-free. In this study, we synthesize the highly active symmetric electrode material Pr_0.32Sr_0.48Fe_0.75Ni_0.2Ru_0.05O_3-δ (PSFNRu) by replacing partial Fe in Pr_0.32Sr_0.48Fe_0.8Ni_0.2O_3-δ (PSFN) with 5 mol% Ru. PSFNRu possesses a sufficient quantity of oxygen vacancies, with the capacity to in-situ exsolved alloy nanoparticles (ANPs) in a reducing atmosphere. This nanocomposite is found to promote electrochemical reactions. For example, at 800 °C, the SSOFC employing the PSFNRu electrode achieves a peak power density (PPD) of 736 mW cm^-2 when using hydrogen (H₂) as the fuel. Under ammonia (NH₃) conditions, the cell delivers a PPD of 547 mW cm^-2, significantly surpassing the 462 mW cm^-2 recorded for a comparable cell employing the PSFN electrode. The enhanced cell performance is mainly ascribed to Ru doping, which boosts the ORR activity and facilitates the in-situ exsolution of ANPs at the anode, increasing active sites and accelerating NH₃ decomposition. In addition, remarkable operational stability of the single cell (172 h under NH₃ fuel at 700 °C) is also demonstrated. These encouraging experimental results highlight the superiority of PSFNRu as the bi-functional electrodes for direct ammonia symmetric solid oxide fuel cells (DA-SSOFCs), and providing a potential and reliable pathway towards accelerating the development of DA-SSOFCs.