New Sr2FeMo0.5X0.5O6 (X=Ni, Co, Mn, Zn) cathodes for proton-conducting SOFCs

Transition metal elements were employed to customize the standard Sr2Fe1.5Mo0.5O6 (SFM) material, with the goal of improving the performance of the SFM cathode in proton-conducting solid oxide fuel cells (H–SOFCs). Sr2FeMo0.5X0.5O6 (X = Ni, Co, Mn, Zn) materials were prepared, but it was discovered that only the dopants Ni and Co can form a pure phase, whereas the dopants Mn and Zn produced an obvious secondary phase. When comparing oxygen vacancies and oxygen diffusion kinetics, utilizing the Co-dopant exhibited clear advantages. The Co-doped SFM had a higher oxygen vacancy content and faster oxygen diffusion kinetics than both the standard and Ni-doped SFM cathodes. The energy barrier for the oxygen reduction reaction (ORR) at the Co-doped SFM cathode was 0.76 eV, which was much lower than that for the SFM and Ni-doped SFM, which were 5.52 and 2.28 eV, respectively. As a result, the Co-doped SFM's cathode reaction was greatly accelerated, resulting in a high fuel cell performance of 1306 mW cm−2 at 700 °C. This finding suggests that using the appropriate dopant can alleviate the low-performance problem of the traditional SFM cathode, resulting in a promising cathode option for H–SOFCs.