Large ambient temperature changes (-20->25 °C) bring great challenges to the purification of the indoor pollutant formaldehyde. Within such a large ambient temperature range, we herein report a manganese-based strategy, that is, a mullite catalyst (YMn2O5) + ozone, to efficiently remove the formaldehyde pollution. At -20 °C, the formaldehyde removal efficiency reaches 62% under the condition of 60,000 mL gcat-1 h-1. As the reaction temperature is increased to -5 °C, formaldehyde and ozone are completely converted into CO2, H2O, and O2, respectively. Such a remarkable performance was ascribed to the highly reactive oxygen species generated by ozone on the YMn2O5 surface based on the low temperature-programed desorption measurements. The in situ infrared spectra showed the intermediate product carboxyl group (-COOH) to be the key species. Based on the superior performance, we built a consumable-free air purifier equipped with mullite-coated ceramics. In the simulated indoor condition (25 °C and 30% relative humidity), the equipment can effectively decompose formaldehyde (150 m3 h-1) without producing secondary pollutants, rivaling a commercial removal efficiency. This work provides an air purification route based on the mullite catalyst + ozone to remove formaldehyde in an ambient temperature range (-20->25 °C).
Keywords: formaldehyde decomposition; mullite oxide; ozone; ultra-low-temperature catalysis.