Influence of photodeposition time and loading amount of Ag co-catalyst on growth, distribution and photocatalytic properties of Ag@TiO2 nanocatalysts

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The activity of different wt% Ag co-catalyst over TiO2 surface under varying UV illuminations (30, 60 and 90 min) for the photodegradation of salicylic acid has been studied. A considerable red shift in the plasmon band was observed with a significant color change (white to light brown) with increased photodeposition time (30–90 min) of Ag over TiO2. Further, the elemental mapping confirms a continuous increase in the wt% of Ag with increased deposition time from 30 min (0.21 wt%) to 90 min (1.69 wt%). These 1, 3 and 5 wt% Ag deposited nanocatalysts prepared at 90 min duration showed higher activity for the photodegradation of salicylic acid under UV light irradiation compared to their counter parts of 30 and 60 min. The higher rate constant (k = 2.73 × 10−2 min−1) value shown by (5 wt% Ag)90@TiO2 is appreciably higher compared to (1 wt% Ag)90@TiO2 (k = 2.29 × 10−2 min−1) and (3 wt% Ag)90@TiO2 (k = 2.33 × 10−2 min−1) photocatalyst and followed pseudo first order kinetics. The maximum activity of (5 wt% Ag)90@TiO2 catalyst has been credited to higher size, number and distribution of Ag co-catalyst nanoparticles over TiO2 surface which greatly vary with change in amount and photodeposition time of Ag nanoparticles.