Catalytic oxidation of CO over the MOx – Co3O4 (M: fe, mn, cu, ni, cr, and Zn) mixed oxide nanocatalysts at low temperatures

A set of mixed metal oxide catalysts, MO_x-Co₃O₄ (M: Fe, Mn, Cu, Ni, Cr, and Zn) enveloped in polymer nanofilms was fabricated using the solid-phase synthesis method. These catalysts were subsequently studied for their catalytic performance in the low-temperature oxidation of carbon monoxide. Characterization of the catalysts was accomplished using various techniques, including X-ray diffraction (XRD), N₂ adsorption-desorption, temperature-programmed reduction (H₂-TPR), temperature-programmed desorption of oxygen (O₂-TPD), Fourier transform infrared spectroscopy (FTIR), thermogravimetric and differential thermal analyses (TGA and DTA) and scanning electron microscopy (FESEM). The outcomes of these investigations indicated that the composite oxides possess different characteristic features. The catalytic activity of these catalysts exhibited a decreasing trend as follows: Fe-Co > Mn-Co > Cu-Co > Ni-Co > Zn-Co > Cr-Co. Among the catalysts prepared, Fe-Co nanoparticles revealed the greatest specific surface area (138 m².g^{- 1}) and the largest pore volume (0.45 cm³.g^{- 1}), resulting in the most superior catalytic activity, achieving total CO conversion at 72 °C. Additionally, the Fe-Co catalyst demonstrated exceptional long-term stability at low temperature (60 °C). Furthermore, the study investigated the impact of various parameters such as calcination temperature, CO content, gas hourly space velocity (GHSV), and pretreatment conditions.