Herein CuO nanoparticles (NPs) with nanostructures were prepared by precipitation method using hydrate copper sulfate (CuSO₄.5H₂O) and sodium hydroxide followed by heat treatment at 400 °C. The as-prepared CuO NPs with nanostructures were investigated using X-ray diffraction (XRD), Fourier Transformed Infra-red spectroscopy (FTIR), Raman spectroscopy, Scanning electron microscopy (SEM), X-ray photochemical spectroscopy (XPS), Energy dispersive spectroscopy (EDS), and Ultra-violet-visible (UV-vis) spectroscopy. In order to evaluate the reducibility, temperature programmed reduction (H₂-TPR) was applied. More importantly, CuO NPs was successfully tested as catalyst towards the total conversion of carbon monoxide (CO) and toluene (C₇H₈). Both XRD and Raman analysis as well as FTIR show that the sample exhibited a monoclinic spinel structure. SEM images indicate that CuO NPs are well-covered by grains size exhibiting homogeneous morphology composed of very fine interconnected particles with an apparent porosity. The sample was made up of Cu and O, according to the XPS and EDS measurements. The band gap energy obtained from optical property analysis is ∼2.65 eV. The catalytic performances of CuO NPs can be assigned to the combined effects of crystal structure, morphology, surface oxygen mobility, redox property and the higher specific surface area (∼87 m²/g). More precisely XPS and H₂-TPR data suggests that, the conversion of CO and C₇H₈ over CuO NPs follows a Mars-van Krevelen type mechanism. More importantly CuO NPs catalysts is reusable and exhibited good stability in the prolonged isothermal test. Thus, CuO NPs is confirmed as an efficient and inexpensive catalysts for CO and C₇H₈ conversion at low temperatures.

Co₃O₄, MgCo₂O₄ and MgO materials have been synthesized using a simple co-precipitation approach and systematically characterized. The total conversion of toluene to CO₂ and H₂O over spinel MgCo₂O₄ with wormlike morphology has been investigated. Compared with single metal oxides (Co₃O₄ and MgO), MgCo₂O₄ with the highest activity has exhibited almost 100% oxidation of toluene at 255 °C. The obtained results are analogous to typical precious metal supported catalysts. The activation energy of toluene over MgCo₂O₄ (38.5 kJ/mol) is found to be much lower than that of Co₃O₄ (68.9 kJ/mol) and MgO ((87.8 kJ/mol)). Compared with the single Co and Mg metal oxide, the as-prepared spinel MgCo₂O₄ exhibits a larger surface area, highest absorbed oxygen and more oxygen vacancies, thus highest mobility of oxygen species due to its good redox capability. Furthermore, the samples specific surface area, low-temperature reducibility and surface adsorbed oxygenated species ratio decreased as follows: MgCo₂O₄ > Co₃O₄ > MgO; which is completely in line with the catalytic performance trends and constitute the reasons for MgCo₂O₄ high excellent activity towards toluene total oxidation. The overall finding supported by ab initio molecular dynamics simulations of toluene oxidation on the Co₃O₄ and MgCo₂O₄ suggest that the catalytic process follows a Mars–van Krevelen mechanism.

Cu and Fe co-doping effect on the structural, optical energy band gap, and catalytic performance as well as recycling stability of Co ₃ O ₄ NCs and their synergetic influence in the toluene deep oxidation via intrafacial process is established.