Critical review of catalytic degradation of formaldehyde via MnO2: From the perspective of process intensification

As a main indoor air pollutant, formaldehyde (HCHO) can harm human health, so the catalytic oxidation of HCHO has attracted great attention in recent years. Manganese dioxide (MnO2) has been widely investigated due to its various valence states, morphological structures, crystal forms, strong HCHO catalytic performance and thermal stability, which can effectively degrade HCHO into harmless CO2 and H2O. From the perspective of process intensification of mass transfer and reaction performance, this review summarizes research progress on key structures and parameters influencing MnO2 mass transfer and reaction performance for degrading HCHO, such as morphological structure, crystal form, surface defect and catalytic stability. Moreover, the reaction mechanism of HCHO oxidation by different MnO2 is also reviewed. Finally, future challenges and research directions of nanostructured MnO2 materials are presented, which could provide basic guidance for appropriate design and preparation of efficient MnO2 materials in integrated environmental applications.