Improved electrochemical performance of Ag-modified Bi0.7Sr0.3FeO3 cathodes by electroless plating for intermediate-temperature solid oxide fuel cells

The Bi_0.7Sr_0.3FeO_3-δ (BSFO)-Ag composite cathode is prepared by modifying BSFO with in-situ chemical plating of Ag. The plated Ag effectively reduces the polarization resistance (R_p) of BSFO. At the Ag loading of 20 wt%, the optimized R_p of BSFO at 650 °C in air condition is 0.35 Ω cm², which is only 18.6 % of that of BSFO cathode (1.88 Ω cm²). The electrochemical performance improvement is primarily attributed to the low oxygen adsorption energy (E_ads) domain at the interfaces of BSFO-Ag, as indicated by the first-principles calculations (E_ads, −0.81eV). Thus, the addition of Ag changes the cathodic reaction rate control step from the molecular oxygen on the cathode surface adsorption and diffusion to charge transfer on the cathode. The maximum power density (P_max) of the prepared single cell at 650 °C is 450.98 mW cm⁻² using H₂ (∼3 vol% H₂O) as fuels. The open-circuit voltage (OCV) does not decay significantly (around 0.66 V) after 50 h at the current density of 400 mA cm⁻², showing good long-term stability.