An infrared study of co-adsorption of N2O and CO on ZnO

The absorption of N(2)O and CO at room temperature on finely divided ZnO surfaces gives reversible absorption bands from surface N(2)O species in the 2237-2245, 2265-2285 and 1245-1255 cm(-1) regions. The growth of the first band is at the expense of the second while its intensity and position depends on the extent of the surface carbonate, formed by the oxidation of CO by N(2)O. The order of introduction of CO and N(2)O, and whether the ZnO surface is oxidised or reduced, gave significantly different results in terms of carbonate formation. The strongest carbonate formation and implied decomposition of N(2)O, occurs at room temperature when CO is added to preadsorbed N(2)O on an oxidised ZnO surface. A single bidentate carbonate is formed under these conditions but on heating in the gas mixture to 200 degrees C an additional, possibly monodentate, carbonate occurs together with a surface formate species.