Ba0.5Sr0.5Fe0.8Sb0.2O3-δ- Sm0.2Ce0.8O2-δ bulk heterostructure composite: A cobalt free Oxygen Reduction Electrocatalyst for low-temperature SOFCs

Low-temperature operated ceramic fuel cells (LT-CFCs 350° to 550 °C) hold a great promise than high-temperature solid oxide fuel cells (HT-SOFCs ≥ 800 °C) for numerous large-scale real-application. If a suitable cathode should be developed to overcome the sluggish oxygen reduction activity at low temperatures, the low-temperature operation of ceramic fuel cells could be possible. In this study, we have developed a cobalt-free Ba0.5Sr0.5Fe0.8Sb0.2O3-δ- Sm0.2Ce0.8O2-δ (BSFSb- SDC) a bulk heterostructure composite for efficient ORR electrocatalyst for LT-SOFC cathode. The established BSFSb-SDC bulk heterostructure composite exhibits large lattice parameters, very low-area-specific resistance, and high oxygen reduction reaction (ORR) activity at low operating temperatures. The prepared fuel cell device has demonstrated high-power densities of 890 mW-cm-2 at 550 °C for button-sized SOFC on H2 and even possible operation at 400 °C. It is also found that BSFSb-SDC effectively facilitates small polaron hopping of valence electrons and diffusion of oxygen ions. Various spectroscopic measurements such as X-ray photoelectron, UV–visible, Raman, and Density Functional Theory (DFT) calculations were employed to understand the improved ORR electrocatalyst function of BSFSb-SDC bulk heterostructure composite SOFC cathode. The results can further help to develop functional cobalt-free electro-catalysts for LT-SOFCs and other related applications.