Oxidation of HCN on the Pt(111) and Pt(112) Surfaces

The adsorption and reaction of HCN on the oxygen-precovered Pt(111) and Pt(112) surfaces have been studied with TPD, AES and LEED measurements in the temperature range from 87 to 1100 K. The adsorbed atomic oxygen was produced by dosing 18O2at 300 K. Besides the usual recombination products (H2, HCN and C2N2), the reaction with oxygen gives H2O, CO, CO2, N2 on both surfaces and some NH3 on the Pt(112) surface. The product yields were measured as a function of initial oxygen coverage, and considerable yield changes were observed as O-precover-age was increased. The HCN dissociation was favored on the Pt(112) surface resulting in more recombination and more oxidation products compared to Pt(111). The selectivity for the oxidation process was found to be higher for Pt(111) than for Pt(112). All the atomic oxygen could be consumed completely during the reaction on both surfaces. It is proposed that the oxidation of CN groups on the platinum surface is through an NCO intermediate.