Microstructural study of the CO2 absorption in SrxCa1-xFe0.5Co0.5O3-delta

The absorption of CO2 in SrxCa1-xFe0.5Co0.5O3-delta perovskite (x = 0.95, 0 .5) has been studied with the aid of Fe-57 Mossbauer Spectroscopy. Due to t heir remarkable CO2 absorption capability at high temperature, Sr,Ca, Fe0.5 Co0.5O3-delta-type compounds may find application in reducing the industria l CO2 output that is a major source of the global green house effect. The M ossbauer spectra of Sr0.5Ca0.5Fe0.5Co0.5O3-delta and Sr0.95Ca0.05Fe0.5Co0.5 O3-delta were markedly different before as well as after CO2 absorption, in dicating different microenvironments and electronic structure of the Fe ato ms in the lattice. The Ca-rich compound absorbed CO2 much faster and had tw ice as much total CO2 absorption capacity than the other one. The high abso rption rate was attributed to the orthorhombic layered brownmillerite struc ture of Sr0.5Ca0.5Fe0.5Co0.5O3-delta, while it was concluded that the cubic structure of Sr0.95Ca0.05Fe0.5Co0.5O3-delta, stabilized by higher O-stoich iometry, is unpreferred for CO, absorption. In agreement with X-ray diffrac tion (XRD) data, the reaction 2(Sr,Ca)(Fe,Co)O-2.5 + CO2 --> (Sr,Ca)CO3 + ( Sr,Ca)(Fe,Co)(2)O-4 is proposed to account for the absorption process. (C) 2001 Elsevier Science B.V. All rights reserved.