Thermal decomposition of CO on a stepped Ni surface

The adsorption-desorption behaviour of CO on the stepped Ni(S) 5(111) × (11̄0)] and the smooth Ni(111) plane are compared by using LEED, thermal flash desorption and AES. Above room temperature flash desorption from the Ni(111) face yields a single α peak characteristic of molecularly adsorbed CO whereas from the stepped surface in addition to the a peak α second desorption peak (β2) appears around 550°C which is assigned to associative CO desorption. If carbon and oxygen are separately chemisorbed on Ni(111) associative desorption of CO leads to a desorption peak around 350° C. It is concluded that steps lower the activation energy for CO decomposition but increase the activation energy for associative desorption.