SURFACE NITRIDE FORMATION ON SUPPORTED COPPER-CATALYSTS AND ITS INTERACTION WITH CO

Supported copper produced by hydrogen reduction of nitrate impregnated silica may retain sufficient nitrogen to inhibit CO adsorption at room temperature. XPS results indicate that the nitrogen is present in a nitride-like form. The deactivating effect of preadsorbed N atoms on CO chemisorption has been studied by volumetric and surface potential measurements on polycrystalline copper films. An N coverage of 0. 1 hardly affects the CO adsorption capacity or the sp behaviour at 77 K, but the heat of adsorption is substantially reduced on the whole surface. With increasing N coverage the low temperature behaviour progressively changes to give a much larger positive CO sp. This behaviour is consistent with single crystal studies and it is attributed to reduced interaction with the copper surface d-band.