Enhanced reactivity of adsorbed oxygen on Pd(111) induced by compression of the oxygen layer -: art. no. 155414

The reaction between O atoms and CO molecules on Pd(111) was investigated by scanning tunneling microscopy (STM). CO was dosed on the (2x2)O-covered surface at temperatures between 100 and 190 K, and the structure changes were monitored by STM. CO adsorption causes compression of the (2x2)O overlayer into islands of the (2x1)O structure, followed by reaction of the O atoms to give CO2. The (2x2)O overlayer does not react with CO at temperatures up to 180 K, whereas the (2x1)O phase reacts at temperatures as low as 136 K. The analysis of the reaction kinetics reveals an activation energy for the O+CO reaction of 0.4 eV and a reaction order of 1 with respect to the O coverage.