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. = 100m2 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 °C, assigned as CeO2–Co3O4–R200 and CeO2–Co3O4–R400 and calcination (under 350 and 550 °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 °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. = 109m2 g−1) and the main phase was CeO2,Co3O4 and CoO. While, the CeO2–Co3O4–R400 binary oxide exhibited lower surface area (S.A. = 40m2 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.