Exploring the mechanism of NO-C_2H_4 reactions on the surface of stepped Pt(332)

摘要

Fourier transform infra red reflection-absorption spectroscopy (FTIR-RAS), thermal desorption spectros-copy (TDS), and Auger electron spectroscopy (AES), were employed to explore the mechanism of NO reduction in the presence of C_2H_4 on the surface of stepped Pt(332). Both NO-Pt and C_2H_4-Pt interactions are enhanced when NO and C_2H_4 are co-adsorbed on Pt(332). As a result, C_2H_4 is dissociated at surface temperatures as low as 150 K, and the N-0 stretch band is weakened. The presence of post-exposed C_2H_4 leads NO desorption from steps to decrease significantly, but the same effect on NO desorption from terraces becomes appreciable only at higher post-exposures of C_2H_4, e.g., 0.6 L and 1.2 L, and proceeds to a much slighter extent. Auger spectra indicate that as a result of the reaction with O from NO dissociation, the amount of surface C species is greatly reduced when NO is post-exposed to a C_2H_4 adlayer. It is concluded that reduction of NO in the presence of C_2H_4 proceeds very effectively on the surface of the Pt(332), through a mechanism of NO dissociation and subsequent O removal. Following this mechanism, the significant dissociation of adsorbed NO molecules on steps at surface temperatures below 400 K, and subsequent rapid reaction between the resultant O and C-related species, accounts for the considerable amount of N_2 desorption at temperatures below 400 K.