Effect of Time and Amount of Ag Photodeposition over TiO2 on Photo Catalytic Properties

Abstract

This work investigate the influence of amount (1-5 wt %) and time (30-90 min) of Ag cocatalyst photodeposition over TiO2 on the photocatalytic activity of different Ag-TiO2 nanocatalysts for the degradation of salicylic acid under UV light irradiation. A considerable red-shift in the plasmon band (454 to 552 nm) with a significant color change (white to brown) of various Ag-TiO2 nanocomposites were observed with increasing time and amount of Ag deposition over TiO2 surface. It was also observed that the average hydrodynamic size 344 nm of bare TiO2 is increased to 782 nm for (5 wt % Ag)90 min -TiO2 due to higher amount of Ag loading during 90 min. The EDX-mapping revealed higher amount (1.69 wt %) of Ag deposition during 90 min as compared to 0.21 wt % Ag after 30 min UV light irradiation. These 1, 3 and 5 wt% (Ag)90 min-TiO2 nanocatalysts always showed better photocatalytic activity (rate constant k = 2.73 × 10-2 min-1) than 1 wt % (Ag)30/60 min -TiO2 composites ( k = 0.95 × 10-2 min-1) for the degradation of salicylic acid under UV light irradiation. Thus different photoactivity of 1-5 wt% Ag-TiO2 nanocatalysts are correlated with the size and nature of Ag co-catalyst distribution over TiO2 surface as a function of time and the amount of Ag deposition under UV light irradiation.