Electronegative Modifiers Effect on the Dissociative NO Adsorption

The same trends regarding the effect of sulfur have been reported for NO adsorption on Pt(lOO)90 and Rh(100).6 In the case of Pt(100) dissociative adsorption is completely inhibited upon formation of a p(2x2) overlayer at a sulfur coverage equal to 0.25, while the binding strength of molecularly adsorbed NO is lowered by more than 50 kJ/mol, as calculated by analysis of NO TPD data. Due to this complete inhibition of dissociative adsorption, the CO+NO reaction is completely deactivated, although it proceeds easily on sulfur free Pt(100). In the case of Rh(100) a sulfur coverage of only 0.08 suffices to completely inhibit NO dissociation at 300 K. 

This observation is directly related to the observed dramatic electrochemical promotion of NO reduction by CO and C3H6 in presence of 02 on Rh/YSZ upon electrochemical O2 supply to the Rh catalyst surface (Fig. 2.3 and Chapters 4 and 8). 

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