The relationship between surface open cells of α-MnO2 and CO oxidation ability from a surface point of view

alpha-MnO2 is a widely reported material for catalysis reactions. However, due to its complicated structure with 2 x 2 tunnels, knowledge of the surface structure and its relationship with the catalytic performance for alpha-MnO2 is limited, even though the understanding of this is key for developing better catalysts. Herein, a surface-focused structure-performance relationship regarding the oxidation of CO is established in this work. It is shown that the 2 x 2 tunnels are open at the surface {100} planes via transmission electron microscopy (TEM), TEM simulation, and CeO2 probe deposition experiments. Since alpha-MnO2 is rod-like and wrapped with {100} planes, the surface of alpha-MnO2 consists mainly of this open cell structure. The open cells are rich in adsorption sites for O-2. Furthermore, these surface sites are also highly oxidative in nature. Owing to the fact that CO can react with surface oxygen species to yield CO2, the promoted adsorption of O-2 and the oxidative surface sites will benefit CO oxidation over alpha-MnO2. Thus, the superior performance for CO oxidation can be related to the open cell structure. This work not only establishes the surface structure-performance relationship, but also provides a new point of view for the understanding of the structure of alpha-MnO2 by emphasising the surface open cells.