Temperature and pH effect on reaction mechanism and particle size of nanostructured Co₃O₄thin films obtained by sol-gel/dip-coating

This article reports the preparation of Co3O4 phase films by sol-gel. Initially, the precursor solution was prepared by the reaction of cobalt acetate tetrahydrate with methanol. Clean glass substrates were dipped into the solution for 4 times with a speed of dipping of 2 cm per minute. Afterwards, the films deposited were thermally treated at 500 °C to produce the Co3O4 phase. FTIR, UV-Vis and XRD techniques were used to analyze the effects of temperature and pH on reaction carried out on the precursor solution. While the microstructural characterization of thermally treated films was performed through XRD and SEM techniques. In parallel, were studied the thermal decompositions of both Co(CH3COO)2 phase as precursor solution S2 powders using TGA-DTA techniques. The results show that Co3(CH3COO)5OH phase was identified as the precursor to the Co3O4 phase. It was observed that the synthesis temperature promotes the formation reaction of Co(CH3COO)5OH. While the decrease in pH by addition of citric acid had 2 effects. The first was to delay the formation reaction, and the second was to decrease the particle size of phase Co3O4 < 10 nm.