SPECTROSCOPIC EVIDENCE FOR ADSORPTION SITES LOCATED AT CU ZNO INTERFACES/

FTIR spectra are reported of CO and formic acid adsorption on a series of Cu/ZnO/SiO2 catalysts. Peaks due to linear CO adsorbed on copper d iminished in intensity as the loading of ZnO was increased. This behav iour was explained in terms of ZnO island growth on the copper surface . Similarly, reduction of the copper concentration while maintaining a constant ZnO loading also resulted in further attenuation in bands as cribed to CO chemisorbed on copper. Formic acid exposure to a Cu/SiO2 sample produced a formate species displaying a v(as)(COO) mode at 1585 cm(-1). Addition of a small quantity of ZnO to the catalyst resulted in substantial promotion of formate growth, which was accompanied by a shift (and broadening) of the v(as)(COO) vibration to 1660-1600 cm(-1 ). Since further ZnO incorporation poisoned formate creation it was co ncluded that formate species bonded to Cu and Zn sites located at inte rfacial positions had been formed. Tne role of such species in methano l synthesis is discussed.