CO₂ decomposition using metal ferrites prepared by co-precipitation method

Abstract

To catalytically decompose the greenhouse gas, CO₂, spinel structure M-ferrites (M=Co, Ni, Cu, Zn) were synthesized by chemical co-precipitation using metal salts and sodium hydroxide as starting materials. The crystallite size of the newly-prepared M-ferrites increased and the BET surface area decreased with increasing calcination temperature. A thermal analysis of the reduction and reoxidation of M-ferrites indicated that substitution of divalent transition metals (i.e., Cu, Ni and Co) into Fe₃O₄ improved the reduction kinetics in the order of Cu>Ni>Co. ZnFe₂O₄ was the most difficult compound to completely reduce due to its stable structure. Commercial samples of the reduced Fe₃O₄, CoFe₂O₄ and ZnFe₂O₄ showed an increase in mass through the reoxidation process, but it was much more difficult for oxygen atoms to enter the structure of the reduced samples of NiFe₂O₄ and CuFe₂O₄. The M-ferrites in a batch type reactor showed better efficiency than the commercial Fe₃O₄. Also found was that CoFe₂O₄ showed a high regeneration potential, although it required a higher critical reaction temperature. NiFe₂O₄ and CuFe₂O₄ were excellent candidate materials for CO₂ decomposition at lower temperatures.