Theoretical and Experimental Investigations on K-doped SrCo_0.9Nb_0.1O_3-δ as a Promising Cathode for Proton-Conducting Solid Oxide Fuel Cells

Improving proton conduction in cathodes is regarded as one of the most effective methods to accelerate the sluggish proton-involved oxygen reduction reaction (P-ORR) for proton-conducting solid oxide fuel cells (P-SOFCs). In this work, K⁺ dopant was used to improve the proton uptake and migration ability of SrCo_0.9Nb_0.1O_3-δ (SCN). K⁺-doped SCN (KSCN) demonstrated great potential to be a promising cathode for P-SOFCs. Density functional theory calculations suggested that doping with K⁺ led to more oxygen vacancies and more negative values of hydration enthalpy, which was helpful for the improvement of proton concentration. Importantly, the proton migration barriers could be depressed, benefiting proton conduction. Electrochemical investigations signified that the cell using KSCN cathode had a peak power density of 967 mW cm⁻² at 700 °C, about 54.1 % higher than that using a SCN cathode. This research highlights the K⁺-doping strategy to improve electrochemical performance of cathodes for P-SOFCs.