Designed preparation of nano rod shaped CeO2-MnOx catalysts with different Ce/Mn ratios and its highly efficient catalytic performance for chlorobenzene complete oxidation: New insights into structure–activity correlations

Abstract

Series of nano rod shaped CeO2-MnOx catalysts with different Ce/Mn molar ratios were synthesized through facile hydro-thermal method and subjected to chlorobenzene (CB) complete catalytic oxidation tests. Detailed structural/chemical characterizations such as TEM/HRTEM, Rietveld XRD, N2 adsorption/desorption, UV-Raman and H2-TPR were conducted. Results show that the designed nano rod shaped CeO2-MnOx binary oxides can be promising with highly efficient catalytic performance towards the complete oxidation of CB. The Ce/Mn-1/8 catalyst (Ce/Mn molar ratio 1:8) is verified as the most outstanding candidate among all the CeO2-MnOx catalysts obtained, which not only presents best catalytic activity but also gives less production of hazardous polychlorinated byproducts, along with excellent durability. Further characterizations reveal that such catalytic advantages can be attributed to both the unique morphology effect and the Ce-Mn strong interaction in the nano rod shaped CeO2-MnOx catalysts. The designed nano rod shaped CeO2-MnOx catalyst mainly exposes the more defective {1 0 0} facet, generating lattice micro-strain and favorable for forming more oxygen vacancies. While the formation of todorokite/vernadite phase with special tunnel-like structure which promoting the migration of lattice oxygen to catalyst surface. Moreover, the strong interaction between CeO2 and MnOx can promote the (Ce4+/Ce3+ ↔ Mn4+/Mn3+) redox cycles and is beneficial for CB deep oxidation. Increasing Mn content leads to higher content of todorokite/vernadite phases, surface Mn4+ enrichment and shorter nano rods with more exposes lattice defects, thus rendering enhanced Ce-Mn strong interaction and morphology effect in Ce/Mn-1/8 catalyst.