Cu-Zn-Co nanosized mixed oxides prepared from hydroxycarbonate precursors

Cu/Zn/Co mixed hydroxycarbonates with Cu/Zn atomic ratio = 2.34 and Co atomic percentage variable between 3 and 20% were synthesized by coprecipitation at constant pH. The temperature of the solutions prior to the mixing (RT or 65 °C) and the Co percentage determine the phases of the hydroxycarbonate samples. XRD pattern and IR spectra indicate a malachite-like structure for the samples with 3% and 8% Co. The sample with 14% Co is crystalline, only if prepared with solutions at 65 °C, whereas the 20% Co samples are amorphous, regardless of the preparation temperature. Thermogravimetric analysis is performed to choose the calcination conditions. High surface area mixed oxides are obtained from the hydroxycarbonates by calcination at 350 °C for 3 h. XRD and SEM analyses show that the malachite-like structured precursors yield nanosized mixed oxides with a dominant tenorite-like phase and the amorphous ones give rise to polydispersed or amorphous oxides. EDS maps indicate a homogeneous distribution of the elements in the oxides.