Synthesis Of CO₂SM-modulated MnO₂-based Composites And Study Of Formaldehyde Degradation Properties

Living,studying and working indoors accounts for about 75%of people’s time.Therefore,indoor air quality is critical to human health.Formaldehyde（HCHO）is a typical indoor air pollutant,mainly originating from building materials and decorative materials,etc.HCHO is harmful to the nervous system and cardiovascular system,and the World Health Organization has classified HCHO as the number one human carcinogen.Therefore,it is necessary to develop cheap and highly active formaldehyde degradation catalysts to control formaldehyde concentration.In this paper,ε-Mn O₂@Ce O₂ catalyst was produced by hydrothermal-pyrolysis,and the degradation effect of the catalyst on HCHO was optimized by regulating the preparation conditions.In order to further improve the performance of HCHO degradation,alkali metal potassium doped core-shell structures were prepared through pyrolysis method M-Mn O_x@Ce O₂.The catalyst revealed the reason for its high catalytic oxidation activity through characterization.The density and viscosity of the binary system of 1,2-propanediamine（1,2-PDA）+polyethylene glycol 400（PEG400）were measured.The excess properties of the binary mixture of 1,2-PDA+PEG400 were obtained,and the existence of hydrogen bonds between molecules of the binary system was demonstrated by spectroscopic characterization,and the strongest hydrogen bonding was observed at the alcohol-amine molar ratio of 1:1.On this basis,CO₂ storage materials（CO₂SM）were prepared by capturing CO₂ at a molar ratio of 1:1 for the binary system of 1,2-PDA+PEG400.CO₂SM provided CO₃^2-and structure-directing agents for the preparation of composite catalyst precursors.A mixed solution of Ce³⁺and Mn²⁺and CO₂SM was hydrothermally reacted to produce the Mn CO₃/Ce CO₃OH precursor,which was pyrolyzed to produce the catalystε-Mn O₂@Ce O₂.The optimal preparation conditions of the catalyst were determined based on single-factor and response surface experiments.ε-Mn O₂@Ce O₂ It has a good removal effect on HCHO.When the degradation time is 1 hour and the degradation temperature is30℃,the degradation rate of 10 m L 10 mg/L HCHO solution is 54.9%.When the degradation time reaches 16 hours,the degradation rate is 91.2%.After 10 cycles,the degradation rate remained at 52.3%for 1 hour,indicating good catalyst stability.The series characterization demonstrated thatε-Mn O₂@Ce O₂ is rich in oxygen vacancies and large specific surface area,and therefore exhibits good removal of HCHO.To further enhance the performance of degradation of HCHO,the M-Mn O_x@Ce O₂composite catalyst with core-shell structure was produced by roasting CH₃COOM（where M is an alkali metal）and Mn CO₃/Ce CO₃OH mixture.At the degradation time of 1 h and degradation temperature of 30℃,the degradation rate of M-Mn O_x@Ce O₂ catalyst was94.1%for 10 m L of 10 mg/L HCHO solution,and the degradation rate remained at 82.3%for 1 h after 10 cycles,with good catalyst stability;the degradation rate was 65.8%for 10m L of 40 mg/L HCHO solution,and when the degradation time reached 14 h,the degradation rate was 99.3%.The doping of M significantly enhanced the degradation performance of HCHO at room temperature,changed the activation energy of the reaction,and increased the oxygen vacancies and the adsorbed oxygen species.This study presents a new idea and method for the degradation of HCHO at room temperature,which brings the Mn O₂-based catalyst closer to be used for indoor HCHO degradation.