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 eta1(O) orientation, leading to a shift of the nu(CO) feature to 1650 cm-1. Between 250 and 300 K, an eta2(C,O) form of adsorbed formaldehyde is indicated by a nu(CO) loss feature at 1320 cm-1 in the HREEL spectrum. All formaldehyde species desorbed below 350 K without decomposition.