Methane Combustion over Mesoporous Cobalt Oxide Catalysts: Effects of Acid Treatment

Mesoporous cobalt oxide catalysts synthesized via a nano-replication method were applied to the methane combustion reaction. In addition, samples were treated with different concentrations of nitric acid to modify their surface structures and chemistry. A significant enhancement in the methane oxidation activity was observed for the acid-treated catalysts compared to the pristine catalyst, and the properties of the acid-treated catalyst were investigated in detail using various characterization techniques. In particular, transmission and scanning electron microscopy images revealed a roughening in the surface morphology of the acid-treated catalysts. Meanwhile, the H-2 temperature-programmed reduction results showed that the reducibility of the cobalt oxides was enhanced by the acid treatment. In addition, O-2 temperature-programmed desorption and X-ray photoelectron spectroscopy analyses revealed that the acid-treated catalysts contained larger amounts of surface chemisorbed oxygen than the pristine catalyst, which may explain the enhanced reducibility and oxidation activity of the acid-treated catalysts. In conclusion, simple acid treatment is a useful post-treatment method for the synthesis of highly active bulk oxide catalysts for the methane combustion reaction.