Abstract:
Ultraviolet photoelectron spectroscopy has been used in a comparative study of the catalytic properties of copper and nickel surfaces. Adsorption and decomposition of carbon monoxide, methanol, formaldehyde and methyl formate were examined in the temperature range 78–400 K. Molecular adsorption of methanol and formaldehyde were observed on a copper surface at 295 K and on a nickel surface below 170 K. These molecules were found to interact chemically with the surfaces via oxygen lone-pair orbitals. Successive exposure of both methanol and methyl formate to a copper surface at 295 K caused the formation of adsorbed formaldehyde on the surface and thus any formaldehyde produced was stable at this temperature. On a nickel surface, however, heated to 295 K, both methanol and formaldehyde, exposed to the surface at 78 K, decomposed stepwise removing hydrogen atoms to carbon monoxide and hydrogen. These results are in good agreement with previous kinetic studies on the mechanisms of methanol decomposition on copper and nickel catalysts and therefore provide additional insight into the mechanisms involving the reaction intermediates.
