Preparation of MnO2@MPIA catalysts with a controlled oxygen vacancy for the efficient catalytic oxidation of formaldehyde at room temperature

δ-MnO2 catalysts have attracted much attention because of the abundance of oxygen vacancies (OVs) on the surface to achieve efficient catalytic oxidation of volatile organic compounds (VOCs) such as formaldehyde (HCHO). However, the recycling and regeneration of powdered δ-MnO2 nano-catalysts still limits the practical application of the catalysts. Here, the surface of aramid fiber (MPIA) was treated by corona activation to introduce reactive groups, such as -OH, and -COOH. These reactive groups can promote the exposure of more Mn3+ on the surface of loaded δ-MnO2 to produce OVs. Meanwhile, the strong interactions between the activated MPAI and δ-MnO2 was formed, which helped to improve the stability and cyclic regeneration of the fiber-based δ-MnO2 catalysts. The effects of Mn3+ and OVs on the catalytic performance of δ-MnO2 were targeted and characterized by SEM, XPS and BET. The pathways of HCHO removal by OVs on the δ-MnO2 surface and the relative free energies of the corresponding intermediates were also explored. The results revealed that optimizing the morphology of MPIA surface-loaded δ-MnO2 can obtain a higher concentration of oxygen vacancies, with excellent HCHO removal efficiency at room temperature and high catalytic activity even after multiple cycle regeneration.