Low temperature oxidation of carbon monoxide: the influence of water and oxygen on the reactivity of a Co_3O_4 powder surface

摘要

In this paper, the effect of the presence of humidity and molecular oxygen on the low temperature oxidation of carbon monoxide on a Co_3O4 powder surface was studied. The interaction between the probe molecules and the Co_3O_4 surface was investigated by means of diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy and quadrupolar mass spectrometry (QMS).Carbon monoxide interacts with the Co_3O_4 surface and is converted to carbon dioxide at rather low temperature (T >= 323 K); the formation of carbonate species is also evident. The reactivity of Co_3O_4 is strongly depressed by humidity: as a matter of fact, in steam conditions carbon monoxide oxidation is significant at temperatures higher than 523 K. Moreover, the formation of carbonate species is more evident than in dry conditions. The Co_3C_4 powder surface interacts with oxygen molecules at T >=323 K to originate several activated surface oxygen species. The activation with oxygen does not appear to facilitate significantly the formation of carbon dioxide.