Nitrous oxide decomposition and reduction over copper catalysts supported on various types of carbonaceous materials

Copper supported on three different allotropic forms of carbon materials have been prepared and evaluated as catalysts for the N2O decomposition and reduction reactions. It was found that all the catalysts underwent severe deactivation during the N2O decomposition reaction due to the gasification of carbon substrates. This behavior was particularly evident when activated carbon was used as the support medium. The chemical identity of the active entity involved in the carbon gasification process is believed to consist of a mixture of Cu+ and Cu2+ species and, according to the well established mechanism, the reaction proceeds in such a manner so that the surface of the catalyst undergoes a redox cycle at the gas/solid carbon interface. The introduction of CO into the system was shown to result not only in an enhancement in the activity of the desired N2O decomposition reaction, but also served to inhibit the deleterious carbon gasification process. In addition, this procedure stabilized the copper particles in the metallic state, which is the active species responsible for the dissociation of N2O. Copper dispersed on a diamond substrate appeared to attain the highest activity for the N2O reduction reaction, a feature that is associated with the ability of the metal to undergo a wetting and spreading action on the support surface, possibly resulting in an epitaxial relationship between the two components.