Ce-Fe-Mn ternary mixed-oxide catalysts for catalytic decomposition of ozone at ambient temperatures

Ce-modified Mn–Fe mixed-oxide catalysts were prepared by a citric acid sol-gel method and characterized by X-ray diffraction, Raman, N₂ adsorption-desorption, infrared spectra, H₂ temperature-programmed reduction and thermogravimetric analyses. Their catalytic properties were investigated in ozone (O₃) decomposition reaction. Results show that the small amount of rare earth metal Ce added during Mn–Fe (FM) mixed-oxide synthesis greatly improves the catalytic performance in O₃ decomposition. Among the prepared catalysts, the C_0.04(FM)_0.96 mixed-oxide catalyst exhibits the highest catalytic activity and stability. The O₃ conversion over C_0.04(FM)_0.96 is 98% after 24 h reaction at 25 °C under dry condition, and that over FM decreases to 90% after 16 h reaction. At 0 °C, the O₃ conversion over C_0.04(FM)_0.96 is 95% after 7 h reaction under dry condition, and that over FM slows down to 70%. Under humid condition (RH = 65%), the O₃ conversion over C_0.04(FM)_0.96 is 63% after 6.5 h reaction at 25 °C, while that over FM decreases to 55%. When Ce is doped into Mn–Fe mixed oxides, the small amount of Ce enters the crystal lattice of MnO₂, and partial Fe is separated to form Fe₂O₃. This changes cause lattice distortion and increase defects and enable the as-synthesized Ce–Fe–Mn ternary mixed-oxide catalysts to acquire additional oxygen vacancies and increase their specific surface area, thereby increasing the number of reaction sites and enhancing the catalytic performance of the catalysts forO₃ decomposition.