Abstract
Ag–AgX(X = Cl, Br)@TiO2 nanoparticle-aggregated spheres with different mass ratio of R = TiO2/Ag(X) from 35:1 to 5:1 were synthesized by a facile sol–gel technique with post-photoreduction. The photocatalytic activities of both Ag–AgCl@TiO2 and Ag–AgBr@TiO2 under visible light are effectively improved by ~3 times relative to TiO2 NPAS under the simulated sunlight for the decomposition of methyl orange (MO). Ag–AgBr@TiO2 showed 30% improvement and less stable in photocatalytic activity than that of AgCl@TiO2. The role of Ag and AgX nanoparticles on the surface of Ag–AgX(X = Cl, Br)@TiO2 was discussed. Ag on these samples not only can efficiently harvest visible light especially for AgCl, but also efficiently separate excited electrons and holes via the fast electron transfer from AgX(X = Cl, Br) to metal Ag nanoparticles and then to TiO2-aggregated spheres on the surface of heterostructure. On the basis of their efficient and stable photocatalytic activities under visible-light irradiation, these photocatalysts could be widely used for degradation of organic pollutants in aqueous solution.
Highlights
As an important photocatalyst, titanium dioxide (TiO2) has been widely used in decomposition of toxic and hazardous organic pollutants, and in water splitting for hydrogen production [1,2,3]
The morphology of Ag–AgBr@TiO2 is similar to that of the TiO2-aggregated spheres, which indicates that the precipitation of Ag–AgBr on the surface of TiO2 does not affect the structure of TiO2 nanoparticles-aggregated spheres (NPAS) and TiO2 NPAS present very good sites to adsorb Ag–AgBr
Some researchers proposed that plasma resonance absorption of metallic Ag on the surface of semiconductor contributes to the effective visible absorption and segregation of electron/hole pairs, which results in the higher photocatalytic activity [9, 11, 12]
Summary
Titanium dioxide (TiO2) has been widely used in decomposition of toxic and hazardous organic pollutants, and in water splitting for hydrogen production [1,2,3]. Because noble metal has a strong electron storage property and large work function, the excited electrons transfer from TiO2 to a noble metal nanoparticle is an ultrafast process [9] This phenomenon improves photocatalytic activity by effective charge separation. AgX [13,14,15,16,17,18,19,20,21,22] and Ag/AgX(X = Cl, Br) have been paid much interest in the design of photosensitive composite materials because of their strong absorption of visible light by their surface plasmon resonance (SPR) and self-sensitization.
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