Coupling nitrosyls as the first step in the reduction of NO on metal surfaces : the special role of rhodium

The adsorption of NO and its coupling to yield N2O2 on Rh(100), Pd(100) and Pt(100) surfaces is analyzed using extended Hueckel calcns. It appears that the Blyholder model is a valid description of the chemisorption of NO on Rh(100). There is substantial weakening of the NO bond on this surface. However, in the case of Pd(100) and Pt(100), the N-O overlap population increases upon chemisorption. For some of the geometries studied, the results indicate that for rhodium surfaces the coupled product has significant N-N double bond character, best described by the 6?Ä electron system, hyponitrite. For rhodium surfaces the dimerization of chemisorbed NO seems to be a viable initial step in the NO redn. mechanism. [on SciFinder(R)]