ADSORPTION AND REACTION OF FORMIC-ACID ON NIO(100) FILMS ON MO(100) - TEMPERATURE PROGRAMMED DESORPTION AND HIGH-RESOLUTION ELECTRON-ENERGY LOSS SPECTROSCOPY STUDIES

Adsorption and reaction of formic acid on well-defined NiO(100) films prepared on Mo(100) have been investigated using combined temperature programmed desorption (TPD)/high resolution electron energy loss spectroscopy (HREELS). A novel approach to HREELS of oxide materials is utilized to acquire spectral data. This approach enables the direct observation of weak loss features due to the excitation of adsorbates without serious interference from intense multiple surface optical phonon losses associated with oxide materials. The results indicate that formic acid initially adsorbs associatively on NiO(100) surfaces at 90 K and undergoes heterolytic dissociation upon heating to > 200 K to form a formate intermediate. The adsorbed formate species is proposed to bond to a cation site via one of the oxygen atoms of the formate in a monodentate configuration. The presence of a dimeric formic acid species is also indicated and a bonding configuration for this species has been proposed.