Oxidation over Cu2O surfaces

Structure Sensitivity in Selective Oxidation of Propene over CU2O Surfaces... 

Typical for the visible reduction process of the sample surface is a reduction front travelling over the entire surface and leading to apparently metallic copper (video pictures). The lifetime of the reduced state is very short ( 1 s). Shortly after the metallic state, a progressing surface re-oxidation coiild be followed by eye as a succession of various colours due to light interference in thin CuaO films of increasing thickness. The maximal surface layer thickness can be estimated by the interference colours [24, 25] of at least 300 monolayers CU2O. 

For the redox mechanism to proceed over a copper-based shift catalyst, the dissociation of water must occur. The thermodynamics of this reaction are sufficiently endothermic, indicating that this is unlikely for a bulk material. Van Her-wijnen and de Jong (236) noted that although the reduction of copper is known to proceed smoothly at 200°C, it is not until 800°C (237) that oxides of copper, CU2O or CuO, can be formed from H2O, although surface oxides could possibly form. 

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