Methoxy radical reaction to formaldehyde on clean and hydroxy radical-covered copper(111) surfaces: a density functional theory study

The ab initio cluster approach has been used to investigate the decompositi on reaction of methoxy radical to formaldehyde catalysed by a copper (111) surface and also to study the influence of co-adsorbed hydroxy species on t he same reaction. Previous experimental studies indicate that the former re action occurs with C-H bond cleavage without the interference of other co-a dsorbed species on the metal surface. However, it has been observed in theo retical works that tilting of the methoxy C-O axis has a marked destabiliza tion effect on the methoxy adsorption energy. This tilting of the methoxy C -O axis is important in the decomposition reaction since it allows one of t he methyl hydrogens to approach the surface. From the results reported in t he present paper, we can predict a lower energy barrier for this reaction w hen hydroxy species are adsorbed on the surface. These findings also indica te that defects such as steps on the surface near to adsorbed methoxy islan ds should lower the energy barrier since the tilting of the methoxy C-O axi s should be smaller. (C) 1999 Elsevier Science B.V. All rights reserved.