B. Ohtani et al., PHOTOACTIVATION OF SILVER LOADED ON TITANIUM(IV) OXIDE FOR ROOM-TEMPERATURE DECOMPOSITION OF OZONE, Journal of photochemistry and photobiology. A, Chemistry, 71(2), 1993, pp. 195-198
Dark and photoinduced decomposition of ozone (O3, approximately 80 ppm
) in air over silver (Ag) or silver(I) oxide (Ag2O) loaded onto commer
cially available titanium(IV) oxide (TiO2) powder was studied using a
flow-type reactor (1.5 dm3 min-1) at room temperature. The relatively
lower catalytic activity of bare TiO2 in the dark was significantly im
proved by the loading of Ag or Ag2O via photodeposition or precipitati
on from an alkaline solution respectively. The enhanced activity was a
ttributed to the thermal reaction with O3 to yield silver(II) oxide (A
gO). Therefore, in the dark, the catalytic activity decreased graduall
y with the formation of AgO, as was indicated by the simultaneous blea
ching of the catalyst surface. During prolonged dark reaction, the tot
al molar amount of O3 decomposed over TiO2-Ag2O catalyst was much larg
er than that estimated on the assumption of a stoichiometric equimolar
reaction of O3 with Ag2O to yield AgO, suggesting the slow thermal de
composition of AgO at room temperature. Photoirradiation of the deacti
vated AgO catalyst recovered the activity via regeneration of purple-g
rey Ag deposits. The recovered high activity was kept almost constant
by photoirradiation. The mechanism of these O3 decomposition processes
is discussed.