Oxygen sorption and desorption properties of Sr–Co–Fe oxide

Abstract

SrCoFeO x has been investigated as a new sorbent for air separation and oxygen removal at high temperatures. X-ray diffraction analysis of a SrCoFeO x sample prepared by liquid citrate method reveals that the sample contains an intergrowth ( Sr 4 Fe 6 - x Co x O 13 ± δ ) , perovskite ( SrFe 1 - x Co x O 3 - δ ) , and spinel ( Co 3 - x Fe x O 4 ) phase. Both oxygen vacancies ( V O ¨ ) and interstitial oxygen ions ( O i ″ ) are involved in the oxygen adsorption and desorption process for SrCoFeO x . Compared with the perovskite-type oxide La 0.1 Sr 0.9 Co 0.9 Fe 0.1 O 3 - δ , SrCoFeO x has stronger structure stability in a reducing environment and it also exhibits a larger oxygen sorption capacity at temperatures higher than 800 ∘ C . Meanwhile, unlike La 0.1 Sr 0.9 Co 0.9 Fe 0.1 O 3 - δ which shows a fast adsorption rate and a slow desorption rate at 900 ∘ C , SrCoFeO x shows a fast desorption rate and slow adsorption rate at the same temperature. X-ray diffraction data reveals that SrCoFeO x samples sintered at 1140 ∘ C have a higher amount of the intergrowth phase than samples sintered at 950 ∘ C due to slow formation kinetics. X-ray diffraction and thermogravimetric analysis of SrCoFeO x samples prepared by the citrate and solid state method show that the synthesis method strongly influences the amount of the three phases in a sample.