Effect of high-valence elements doping at B site of La0.5Sr0.5FeO3-δ

SrFeO3-δ perovskite material is considered as a potential substitute for Ni-based fuel electrodes, while the problem of Sr segregation limits the development of material. Herein, different high-valence elements Ti4+, Nb5+and Mo6+ are gradient doped into La0.5Sr0.5FeO3-δ (LSF) to solve Sr segregation and study the influence mechanism for high valence elements. After the LSF is doped by high-valence elements, the reduction stability and CO2 tolerance are found to be obviously improved in a CO2:CO = 1:1 atm. Under the premise of stability, lower-valence element doping requires less Fe4+ reduction and lattice oxygen to match the charge, therefore, La0.5Sr0.5Fe0.9Ti0.1O3-δ (LSFTi5591) possesses more oxygen vacancies than La0.5Sr0.5Fe0.9Nb0.1O3-δ (LSFNb5591) and La0.5Sr0.5Fe0.9Mo0.1O3-δ(LSFMo5591). Since Ti ions possess a weaker binding force with O ions, LSFTi5591 more easily loses lattice oxygen and generates oxygen vacancies under high-temperature and reduction conditions, which results in stronger CO2 adsorption. Using LSCF-GDC as the oxygen electrode of electrolytic cells, the LSFTi5591 cell (1.35 A cm−2) exhibits higher electrochemical performance than LSFNb5591 (1.18 A cm−2) and LSFMo5591 (1.04 A cm−2) cells due to stronger CO2 adsorption and dissociation in the medium-frequency resistance range.