Preparation and characterization of spinel-type MeFe2O4 (Me = Cu, Cd, Ni and Zn) for catalyst applications

Four kinds of spinel ferrites, MeFe2O4 (Me = Cu, Ni, Zn and Cd), were prepared by so called "selfcombustion method" using nitrates as precursors. The morphological and structural characterization of the ferrite powders have been performed with various techniques: X-ray diffraction (XRD), to determine the phase composition, SEM observations to evaluate nanostructure characteristics, EDAX spectroscopy to evaluate the chemical composition and BET analysis to determine the specific surface area. The ferrite powders have been tested catalytically in combustion reaction of three diluted gases: acetone/air, ethanol/air and methanol/air. The results revealed a pronounced decrease in the combustion temperature when Cu- and Ni-ferrites are used as catalysts. A probable cause was ascribed to multiple valences of Cu and Ni ions which favor a rapid increase in the oxygen ion species adsorbed on ferrite surface. -- Highlights: ► A simple and low cost method was used for preparation MeFe2O4 (Me = Cu, Ni, Zn, Cd). ► XRD and SEM confirm spinel structure and nanosized of crystallites (33–52 nm). ► The metal-type has a strong influence on the minimum combustion temperature. ► CuFe2O4 and NiFe2O4 ferrites show superior catalytic activity. ► The catalytic activity of ferrites is controlled by the O2 ion vacancies.