F. Boccuzzi et E. Guglielminotti, IR STUDY OF TIO2-BASED GAS-SENSOR MATERIALS - EFFECT OF RUTHENIUM ON THE OXIDATION OF NH3, (CH3)3N AND NO, Sensors and actuators. B, Chemical, 21(1), 1994, pp. 27-31
The adsorption and oxidation of ammonia, trimethylamine and nitric oxi
de on Ru/TiO2 and TiO2 have been studied by FTIR spectroscopy. On both
the samples ammonia and trimethylamine are adsorbed at room temperatu
re molecularly on the surface Ti4+ sites. By heating ammonia at T>473
K, water and hydroxyls are produced. The oxidation at 473 K of the tri
methylamine on both the samples leads to the formation of dimethylform
amide and water; the oxidation at T>573 K on pure TiO2 leaves residual
NH and CH(x) groups; on Ru/TiO2 a complete oxidation occurs, leading
to nitrosyl species adsorbed on Ru ions and to nitrate species and wat
er on titania. NO adsorbs molecularly on oxidized Ru/TiO2 samples, wit
h formation of Ru3+-NO surface complexes; on the contrary it does not
adsorb at all as such on pure TiO2. On both the samples, nitrate speci
es on titania are produced by interaction with dry air. The complex of
data presented in the paper indicates that the presence of the Ru as
a metallic activator allows a more complete oxidation of the studied m
olecules, justifying the higher sensitivity.