MnO
2 microspheres with various surface structures were prepared using the hydrothermal method, and Au/MnO
2 catalysts were synthesized using the sol-gel method. We obtained three MnO
2 microspheres and Au/MnO
2 samples: coherent solid spheres covered with wire-like nanostructures, solid spheres with nanosheets, and hierarchical hollow microspheres with nanoplatelets and nanorods. We investigated the properties and catalytic activities of formaldehyde oxidation at room temperature. Crystalline structures of MnO
2 are the main factor affecting the catalytic activities of these samples, and γ-MnO
2 shows high catalytic performance. The excellent redox properties are responsible for the catalytic ability of γ-MnO
2. The gold-supported interaction can change the redox properties of catalysts and accelerate surface oxygen species transition, which can account for the catalytic activity enhancement of Au/MnO
2. We also studied intermediate species. The dioxymethylene (DOM) and formate species formed on the catalyst surface were considered intermediates, and were ultimately transformed into hydrocarbonate and carbonate and then decomposed into CO
2. A proposed mechanism of formaldehyde oxidation over Au/MnO
2 catalysts was also obtained.
相似文献