Synthesis of 8-MnO2 via ozonation routine for low temperature formaldehyde removal

Nowadays, it is still a challenge to prepared high efficiency and low cost formaldehyde (HCHO) removal catalysts in order to tackle the long-living indoor air pollution. Herein, 8MnO2 is successfully synthesized by a facile ozonation strategy, where Mn2 + is oxidized by ozone (O3 ) bubble in an alkaline solution. It presents one of the best catalytic properties with a low 100% conversion temperature of 85 degrees C for 50 ppm of HCHO under a GHSV of 48,000 mL/(g center dot hr). As a comparison, more than 6 times far longer oxidation time is needed if O3 is replaced by O2 . Characterizations show that ozonation process generates a different intermediate of tetragonal fi-HMnO2 , which would favor the quick transformation into the final product 8-MnO2 , as compared with the relatively more thermodynamically stable monoclinic y-HMnO2 in the O2 process. Finally, HCHO is found to be decomposed into CO2 via formate, dioxymethylene and carbonate species as identified by room temperature insitu diffuse reflectance infrared fourier transform spectroscopy. All these results show great potency of this facile ozonation routine for the highly active 8-MnO2 synthesis in order to remove the HCHO contamination. (c) 2024 The Research Center for Eco-Environmental Sciences, Chinese Academy of