Adsorption of Formaldehyde on Nickel Oxide Studied by Thermal Programmed Desorption and High-Resolution Electron Energy Loss Spectroscopy

Formaldehyde adsorption on NiO( 100) ultrathin films grown on a Mo(100) surface has been studied using combined thermal desorption and high-resolution electron energy loss spectroscopies (HREELS). The results show that formaldehyde adsorbs molecularly on NiO( 100) film at 90 K and that concurrent polymerization of formaldehyde occurs extensively in the 90-270 K temperature range. Monomeric formaldehyde is chemisorbed onto Ni cationic sites in the oxygen end-on ~ ' ( 0 ) orientation, leading to a shift of the v(C0) feature to 1650 cm-I. Between 250 and 300 K, an v2(C,0) form of adsorbed formaldehyde is indicated by a v(C0) loss feature a t 1320 cm-I in the HREEL spectrum. All formaldehyde species desorbed below 350 K without decomposition.