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

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 Pr0.32Sr0.48Fe0.75Ni0.2Ru0.05O3-δ (PSFNRu) by replacing partial Fe in Pr0.32Sr0.48Fe0.8Ni0.2O3-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.