SIMS study of the formic acid adsorption on polycrystalline copper and CuCl(111) surfaces

Abstract

The formic acid adsorption on polycrystalline copper and CuCl(111) surfaces at room temperature and above (300-500 K) is studied by static SIMS. Formic acid adsorbs as the surface formate ion on both surfaces. Further decomposition of the formate ion is found to be in favour of the formation of the OCO adspecies on Cu(0) and in favour of OC on Cu(I), indicating that the O-C-O bonding is less stable on Cu(I) than on Cu(0). A general enhancement of all negative secondary ions due to the formate overlayer is observed on Cu(0) but not on Cu(I). The fragmentation of the secondary negative parent-like ion, HCOO-, is stronger on Cu(I) than on Cu(0). Both phenomena are utilized to study the bonding interaction between the formate ion and substrate. A bidentate formate structure which is evidenced on Cu(0) by SIMS is thought to be responsible for the greater electron charge transfer from the formate ion to Cu(0) and thus for the more stable OCO bonding on Cu(0) as compared with that on Cu(I). A monodentate structure of the surface formate on Cu(I) is inferred based on the XPS results as well as the SIMS study. © 1993.