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

Abstract

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-MnOx) 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 ∼1.2eV) based on the density functional theory calculations. The ozone conversion over Fe-MnOx kept 97% after 24h reaction, while it over MnO2 slowed down to 85% under dry condition. Remarkably, under humid condition (RH=60%), the ozone conversion over Fe-MnOx kept 73% after 6h reaction, while ozone conversion over pure MnO2 decreased to 50% within 1h under the conditions of 100ppm inlet ozone concentration and weight space velocity of 660Lg−1h−1. The intermediate peroxide species (O22−) formed on the surface oxygen vacancies of Fe-MnOx 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-MnOx 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.