Isothermal and temperature-programmed oxidation of CH over Pt{1 1 0}-(1×2)

The isothermal oxidation of adsorbed CHa on Pt{1 1 0} has been studied using a supersonic molecular beam system. CHa oxidation was found to be much more facile than Ca oxidation and takes place at surface temperatures as low as 330 K. Over the surface temperature range 350–450 K the gas phase products are CO2 and H2O. We conclusively show that the first step of the reaction is CHa+Oa→COa+Ha and that H abstraction to produce OHa and Ca does not occur. CO2 is produced by the subsequent surface reaction of COa with Oa while H2O is produced by Ha oxidation. An Arrhenius analysis yields values for the pre-exponential factor and activation energy for the CHa+Oa reaction of (2.1±1.5)×10−6 molecule−1 cm2 s−1 and 71±3 kJ mol−1, respectively. We also studied the temperature programmed reaction CHa+Oa reaction and found that the product selectivity is very sensitive to the atomic Oa pre-coverage.