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A‐ and B‐site Codoped SrFeO 3 Oxygen Sorbents for Enhanced Chemical Looping Air Separation
Author(s) -
Dou Jian,
Krzystowczyk Emily,
Wang Xijun,
Robbins Thomas,
Ma Liang,
Liu Xingbo,
Li Fanxing
Publication year - 2020
Publication title -
chemsuschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.412
H-Index - 157
eISSN - 1864-564X
pISSN - 1864-5631
DOI - 10.1002/cssc.201902698
Subject(s) - oxygen , air separation , chemical looping combustion , chemistry , perovskite (structure) , activation energy , oxide , sorbent , oxygen transport , analytical chemistry (journal) , partial pressure , materials science , inorganic chemistry , adsorption , crystallography , chromatography , organic chemistry
Chemical‐looping air separation has numerous potential benefits in terms of energy saving and emission reductions. The current study details a combination of density functional theory calculation and experimental efforts to design A‐ and B‐site codoped SrFeO 3 perovskites as “low‐temperature” oxygen sorbents for chemical‐looping air separation. Substitution of the SrFeO 3 host structure with Ca and Co lowers oxygen vacancy formation energy by 0.24–0.46 eV and decreases the oxygen release temperature. As a result, Sr 1− x Ca x Fe 1− y Co y O 3 (SCFC; x= 0.2, 0.0< y <1.0) spontaneously releases oxygen at 400–500 °C even under a relatively high oxygen partial pressure (e.g. PO2=0.05 atm). Sr 0.8 Ca 0.2 Fe 0.4 Co 0.6 O 3 exhibits a significantly higher oxygen capacity of 1.2 wt % at 400 °C and under a PO2swing between 0.05 and 0.2 atm, when compared to the <0.2 wt % capacity for undoped a SrFeO 3 (SF) and Ca‐doped Sr 0.8 Ca 0.2 FeO 3 (SCF). Electrical conductivity relaxation (ECR) study demonstrates that codoping of Ca and Co lowers the activation energy of oxygen diffusion and surface oxygen exchange by 26.6 or 137.9 kJ mol −1 , respectively, resulting in faster redox kinetics for SCFC than for SCF perovskite. The SCFC oxygen sorbent also exhibits excellent stability for 2000 redox cycles for air separation.