CO2 decomposition to carbon by ultrafine Ni(II)-bearing ferrite at 300 °C

Ultrafine Ni(II)-bearing ferrite (UNF) Ni2+0.36Fe2+0.45Fe3+2.19O4.10 was synthesized with a view to investigating materials with the high reactivity toward CO2 → C decomposition. UNF was prepared by coprecipitation of Ni2+, Fe2+ and Fe3+ with NaOH. The electron micrographs of the UNFs showed their size to be 16–29 nm in diameter. The rate of the H2-reduction of UNF was 3 times faster than that of conventional Ni(II)-bearing ferrite (NF) with the size of 100–200 nm prepared by the wet method. The H2-reduced UNF with the spinel structure revealed the much improved reactivity toward CO2 decomposition. The initial rate and amount of CO2 decomposition for the UNFs were 6.5 and 2.5 times greater than those for NF with the same Ni content at 300 °C. Such high reactivity of UNF is attributed to both the level of activation and surface area in comparison with NF.