Methanol Chemistry on Cu and Oxygen-Covered Cu Nanoclusters Supported on TiO2(110)

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The thermal decomposition of methanol has been studied on TiO2(110) as well as on Cu and oxygen-covered Cu nanoclusters supported on TiO2(110) using temperature programmed desorption (TPD). The sizes of the Cu clusters were characterized by scanning tunneling microscopy (STM). Methanol chemistry on the vacuum-annealed, reduced TiO2 surface itself produces ethylene as the main desorption product. Reoxidation of the TiO2 surface quenches the production of ethylene but also results in a new formaldehyde desorption peak at 870 K. The reactivity of methanol on small Cu nanoclusters (40.2 ± 7.0 A diameter, 12.7 ± 2.4 A height) is minimal, but trace amounts of formaldehyde, CO2, methane and H2 are detected in TPD experiments, demonstrating that the Cu nanoclusters are more active than bulk single-crystal Cu surfaces. On oxygen-covered Cu nanoclusters, methanol reaction produces formaldehyde and CO2 as the major gaseous products as well as H2, water, and methane. The yields of formaldehyde and CO2 increase as the...