Phase transformation in CeO2-Co3O4 binary oxide under reduction and calcination pretreatments

The CeO2-Co3O4 binary oxide was prepared by impregnation of the high surface area Co3O4 support (S.A. = 100m(2)g(-1)) with cerium nitrate (20 wt% cerium loading on Co3O4). Pretreatment of CeO2-Co3O4 binary oxide was divided both methods: reduction (under 200 and 400 degrees C, assigned as CeO2-Co3O4-R200 and CeO2-Co3O4-R400 and calcination (under 350 and 550 degrees C, assigned as CeO2-Co3O4-C350 and CeO2-Co3O4-C550). The binary oxides were investigated by means of X-ray diffraction (XRD), nitrogen adsorption at -196 degrees C, infrared (IR), transmission electron microscopy (TEM), diffuse reflectance spectroscopy (DRS) and temperature programmed reduction (TPR). The results showed that the binary oxides pretreatment under low-temperatures possessed larger surface area. The cobalt phase of binary oxides also was transferred upon the treating temperature, i.e., the CeO2-Co3O4-R200 binary oxide exhibited higher surface area (S.A. = 109m(2) g(-1) and the main phase was CeO2,Co3O4 and CoO. While, the CeO2-Co3O4-R400 binary oxide exhibited lower surface area (S.A. = 40m(2) g(-1)) and the main phase was CeO2, CoO and Co. Apparently, the optimized pretreatment of CeO2-Co3O4 binary oxide can control both the phases and surface area.