Solvothermal Nano-cobalt Oxide And Its Electrochemical Properties

In this paper, the preparation of Co₃O₄ by solvothermal method wasmainly studied. The effect of solvothermal condition on phase,morphology and size of the final product and formation mechanism ofCo₃O₄ were also investigated. The effect of particle size andmonodisperse on its electrochemical performance was tested.The maincontent are as follows:Spinel Co₃O₄ was synthesized by solvothermal method usingCo(NO₃)₂ as cobalt salt, NH₃·H₂O-NH₄Cl as precipitator, mono-dispersedspherical-like Co₃O₄ with the particle size of 15nm could be obtained at160℃for 16h when pH value was 9 using water and n-butanol as solvent,polyethylene glycol as dispersant. The cobalt salts have effect on shapeand size of the product of Co₃O₄. cubic Co₃O₄ with the particle size of20nm and spherical Co₃O₄ with 30nm were prepared with Co(Ac)₂ andCoSO₄ as the source of cobalt, respectively.The formation mechanism of the prepared product was investigatedby IR, X-ray diffraction (XRD) and (TG-DTA). The results showed thatcobalt salts were oxidated into Cobalt hydrotalcite-type compounds firstly,and then transformed to Co₃O₄ Upon the solvothermal treatment. NO₃^-was participant in the oxidation of cobalt salt using Co(NO₃)₂ as cobaltsalt. Its formation of includes two steps:(1) Co(OH)_2-x(NO₃)_x is oxided toCo_1-x^ПCo_x^Ш(OH)_2-y(NO₃)_x+y by H₂O₂.(2) Co_1-x^ПCo_x^Ш(OH)_2-y(NO₃)_x+yistransformed to Co₃O₄ with minor phase of Co(OH)₂. and Co(OH)₂ wasslowly oxidated to Co3O₄ by NO₃^- inseted newly into the layered structure,the pure phase of Co₃O₄ was obtained after 16h.The temperature of precursor prepared with solvothermal method waslower than that of precursor without solvothermal hydrothermal method.The rod-like, polyhedron-like and sheet Co₃O₄ could be obtained bydifferent thermal decomposition methods using various precipitators.The electrochemical performances of the product were alsoinvestigated. The results show that both particle size and monodisperse have effect on its electrochemical performance, the electrochemicalproperty of nano-Co₃O₄ is superior to that of micro-Co₃O₄; and cubicCo₃O₄ has the best electrochemical property in all the as-preparedsamples.