Electric-enhanced hydrothermal synthesis of manganese dioxide for the synergistic catalytic of indoor low-concentration formaldehyde at room temperature

Nowadays, indoor air pollution of low-concentration formaldehyde (HCHO) is threatening seriously human health. In this work, a carbon cloth supported MnOx composite (MnOx-CC) with coaxial cable structure was synthesized as catalysts by electric-enhanced hydrothermal synthesis. The MnOx-CC catalysts showed a flower-liked MnOx nanospheres structure with interconnected nanosheets. During the static testing, the HCHO concentration can be reduced from 7 ppm to 0.074 ppm at 25 ℃, which is below the international guideline values (0.08 ppm). Under the WHSV of ~120,000 mL/(gMnOxh), the removal efficiency was as high as ~97% and the catalyst can keep working for 24 h without an significant drop at room temperature. A novel mechanism – synergistic catalytic effect mechanism of MnOx was proposed to illuminate the catalyst performance. It reveals that the mutual conversion process among different valences of MnO2, Mn2O3 and MnO is critical to the generation of active oxygen and decomposition of intermediates, and they jointly promote the effective degradation of HCHO. This work may provide a new strategy to synthesizing the catalysts for HCHO removal with high efficiency and present an insight for catalytic process of MnOx.