Direct in situ activation of Ag-0 nanoparticles in synthesis of Ag/TiO2 and its photoactivity

Abstract

Metallic Ag nanoparticles (Ag0) were successfully activated using a direct in situ electrochemical method before being supported on TiO2. Catalytic testing showed that 5 wt% Ag–TiO2 gave the highest photodegradation (94%) of 50 mg L-1 2-chlorophenol (2-CP) at pH 5 using 0.375 g L-1 catalyst within 6 h, while under similar conditions, 1 wt% and 10 wt% Ag–TiO2 only gave 75% and 78% degradation, respectively. Characterization results illustrated that the photoactivity was affected by the amount of Ag0 and oxygen vacancies which act as an electrons trap to enhance the electron–hole separation. While, the Agsingle bondOsingle bondTi bonds formation reduced the photoactivity. The degradation followed a pseudo-first order Langmuir–Hinshelwood model where adsorption was the controlling step. Study on the effect of scavengers showed that the hole (H+) and hydroxyl radical (OHradical dot) play important roles in the photodegradation. The regenerated photocatalyst was still stable after five cycling runs.