Optimizing energy conversion in direct carbon fuel cells based on brown coal char: Exploring the impacts of scandium substituted La0.6Sr0.4FeO3-δ anodes

Abstract

Direct coal fuel cells (DCFCs) convert the chemical energy in coal directly into electricity, but their development has been hindered by insufficiently active anode materials and slow carbon oxidation kinetics. This study explores the use of scandium-doped B-site-deficient La_0.6Sr_0.4FeO_3-δ (LSFSc_x, x = 0, 0.05, 0.10, 0.15) as anodes for brown coal char utilization in DCFCs. Our findings show that LSFSc_x (x$\ne 0$) anodes outperform the undoped LSF anode, with the LSFSc_0.1 anode exhibiting the best performance. At 850 °C, the LSFSc_0.1 anode achieves a maximum power density of 345.5 mW cm⁻², a minimum polarization resistance of 0.18 Ω cm², and an impressive discharge time of 13.23 h. These enhancements are attributed to scandium doping, which improves the three-phase reaction boundaries, enhances carbon oxidation through better oxide ion transport, and optimizes the electronic structure. Theoretical calculations indicate that scandium doping reduces the Bader charges of Fe atoms, weakens OFe bonds, lowers the oxygen vacancy formation energy, and maintains the electronic energy band structures. These results provide a new and effective pathway to improve the anode performance and efficiency of DCFCs, showcasing new possibilities for future research on scandium-based perovskite materials for DCFC applications.