Cation-deficient nano-dimensional particle size cobalt–manganese spinel mixed oxides

Cobalt–manganese binary spinel oxides of high-dispersity are synthesized by thermal decomposition of hydroxycarbonate precursors in the limits 0.33≤Mn/Co≤2. The mixed oxides are cation-deficient and contain a high surface concentration of non-stoichiometric oxygen. The oxygen-to-metal surface ratios, determined by ESCA are higher than the stoichiometric value for dioxides. The spinel lattice is tetragonally distorted for atomic ratios Mn/Co>1. The samples synthesized below 400 °C are composed from spherical-shaped particles with diameters in the nano-scale range 6–12 nm. Reduction of the binary spinel oxides with hydrogen proceeds in multiple steps that correspond to the reduction steps Co(III)⇒Co(II); Co(II)⇒Co reduction and Mn(IV), Mn(III)⇒Mn(II). In the temperature range 100–1200 °C reduction to metallic manganese has not been observed.