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

SrFeO3-delta 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-delta (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-delta (LSFTi5591) possesses more oxygen vacancies than La0.5Sr0.5Fe0.9Nb0.1O3-delta (LSFNb5591) and La0.5Sr0.5Fe0.9Mo0.1O3-delta(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.

Automated summary

The gradient doping of high-valence elements into LSF helps to resolve Sr segregation issue and significantly improves the reduction stability and CO2 tolerance of the material. LSFTi5591 exhibits better electrochemical performance due to stronger CO2 adsorption and dissociation compared to LSFNb5591 and LSFMo5591.