Facile synthesis of Fe-modified manganese oxide with high content of oxygen vacancies for efficient airborne ozone destruction

Oxygen vacancy engineering is an efficient strategy to improve the catalytic performance of nanomaterials. In this work, a highly active Fe-modified manganese oxide (Fe-MnO_x) was synthesized and used for airborne ozone decomposition. The addition of Fe³⁺ during MnO₂ synthesis led to higher specific surface area, greatly increased content of oxygen vacancies, evidenced by XPS, H₂-TPR analysis and lower oxygen vacancy formation energy (decreased by ∼1.2 eV) based on the density functional theory calculations. The ozone conversion over Fe-MnO_x kept 97% after 24 h reaction, while it over MnO₂ slowed down to 85% under dry condition. Remarkably, under humid condition (RH = 60%), the ozone conversion over Fe-MnO_x kept 73% after 6 h reaction, while ozone conversion over pure MnO₂ decreased to 50% within 1 h under the conditions of 100 ppm inlet ozone concentration and weight space velocity of 660 L g⁻¹ h⁻¹. The intermediate peroxide species (O₂²⁻) formed on the surface oxygen vacancies of Fe-MnO_x and MnO₂ during ozone decomposition reaction were observed using in situ Raman spectroscopy. The concentration and depletion rate of O₂²⁻ on the surface of Fe-MnO_x was higher than that on MnO₂, illustrating that O₂²⁻ acted as the key species to boost the catalytic process. The content and dispersity of oxygen vacancies were identified to be mainly responsible for the performance difference. This provides a promising idea for designing novel nanomaterial catalyst for gaseous ozone decomposition.