Synthesis of Co3O4 spinel at ambient conditions

Co3O4 was prepared in aqueous solutions through a staged oxidation process. When the mole ratio of starting chemicals Co2+:OH- is less than or equal to 1:2 (Co2+ as a limiting reagent), the formation reaction follows the brucitelike phase to cobalt oxide-hydroxide, and then to cubic spinel. However, when the ratio of Co2+:OH- is >1:2 (OH- as a limiting reagent), the reaction path changes to the brucite-like to hydrotalcite-like phase, and then to the spinel. Using the present method, Co3O4 can be formed at a temperature as low as 40 degrees C, and single-phase spinel Co3O4 can be prepared at 50 degrees C within hours under normal atmospheric pressure.