Flexible A-site doping La_0.6-xM_xSr_0.4Co_0.2Fe_0.8O₃ (M=Ca, Ba, Bi; x=0, 0.1, 0.2) as novel cathode material for intermediate-temperature solid oxide fuel cells: A first-principles study and experimental exploration

To address both challenges of insufficient oxygen vacancies and excessive interface resistance in intermediate-temperature solid oxide fuel cells (IT-SOFCs), in this study, we apply the first-principle density functional study to choose the A-site cation doping M(M = Ca, Ba, Bi) for conventional La_0.6Sr_0.4Co_0.2Fe_0.8O₃ (LSCF) and find that Bi doping could produce the smallest generation energy of oxygen vacancy. Then novel Bi-doped La_0.6-xBi_xSr_0.4Co_0.2Fe_0.8O₃ (LBSCFx, x = 0,0.1,0.2) cathode materials are investigated, revealing Bi³⁺ doping can promote the electrochemical performance of LBSCFx cathode by the enrichment of oxygen vacancies and the triple-phase boundaries. Attributed to the accelerated oxygen transportation and the increased oxygen reduction reaction sites, the effectiveness of Bi³⁺ doping LSCF on the reduction of polarization resistant (R_p) and activation energy (E_a) is superior than most of other LSCF doping strategies. The R_p and E_a values of LBSCF0.2 are reduced more than 58% and 27% compared to that of undoped LSCF respectively, and the maximum power density of the anode-supported single cells based on LBSCF0.2 outperforms 1 W⋅cm⁻² at 750 °C. Both R_p and power density suggest the effectiveness of Bi doping strategy for developing cathode materials in IT-SOFCs.