Complete combustion of methane over Co3O4 catalysts: Influence of pH values

A series of Co3O4 catalysts were prepared at different pH values via a facile precipitation method and their catalytic performances were evaluated for complete methane combustion. The catalysts were characterized by various techniques such as BET, XRD, SEM, XPS, Raman, H2-TPR and NH3-TPD. It is observed that the pH values in the process of preparation significantly influenced the catalytic activity and long-term stability and the Co3O4-9.0 catalyst showed the best performance. The influence of pH values in the methane combustion activity was discussed on basis of the microstructure, surface and reduction properties of catalysts. The superior performance of Co3O4-9.0 catalyst would origin from the higher ratios of ATetrahedral/AOctahedral and Oads/Olatt, although it has the smallest surface area and biggest crystalline size. That is to say, the tetrahedral sites Co2+ concentration and surface active oxygen species play a decisive role for the catalytic activity of methane combustion.