IDENTIFICATION OF THE FIXED NITROGEN-CONTAINING SPECIES DURING THE PHOTOOXIDATIVE FIXATION OF MOLECULAR NITROGEN ON UV-ILLUMINATED TIO(2) SURFACES

Ultraviolet photoexcitation of hydroxylated TiO2 surfaces in the prese nce of a mixture on N2/O2 gas (air) produces some adsorbed nitrogen ox ide species which were previously assigned indirectly as probably N2O2 (2-). Direct assignment is now reported here. From comparisons of the thermodesorption profiles and the XPS results from polycrystalline Na2 N2O2 and from the corresponding data obtained from TiO2 surfaces upon which Na2N2O2 had been allowed to adsorb with the thermodesorption pro file and XPS data obtained from the photo-induced fixation of nitrogen on TiO2, it can be concluded that the principal species formed during the photo-oxidative fixation of molecular nitrogen on TiO2 is hyponit rite anion, N2O2(2-).