Control of surface area and porosity of Co3O4 via intercalation of oxidative or nonoxidative anions in hydrotalcite-like precursors

Monometal hydrotalcite-like compounds of (Co0.74Co0.26III)-Co-II(OH)(2.01)( NO3)(0.21)(CO3) (0.02).0.6H(2)O and (Co0.74Co0.26III)-Co-II(OH)(1.99)(CO3)( 0.13)(NO3)(0.01) .0.7H(2)O have been prepared via precipitation and anion-e xchange methods. After being heated at 150-600 degreesC, the two precursor compounds were oxidatively converted to product spinel Co3O4 The chemical n ature of the anions intercalated in the interlayer space of the compounds d etermines the ultimate crystallite size, surface area, and porosity of the oxide spinel. By selection of carbonate anions, Co3O4 with crystallite size of 7-34 nm and surface area of 17-150 m(2)/g can be prepared at 150-600 de greesC. In particular, nanometer size Co(3)Q(4) crystallites (7-10 nm) has been synthesized at a temperature as low as 150-250 degreesC from the precu rsor compound (Co0.74Co0.26III)-Co-II(OH)(1.99)(CO3)(0.13)(NO3)(0.01) .0.7 H2O. The roles of the different anions in the interlayer space are also dis cussed with respect to the thermal decomposition of the precursor compounds .