A mechanism for enhanced photocatalytic activity of nano-size silver particle modified titanium dioxide thin films

Abstract

Ag-TiO 2 nanostructured thin films with silver volume fraction of 0-20% were deposited on silicon and quartz substrates by RF magnetron sputtering and annealed in ambient air at 950°C for 1 h. The phase structure and surface topography of the films were characterized by X-ray diffractometer and transmission electron microscope. Photocatalytic activity of the films was evaluated by light induced degradation of methyl orange (C 14 H 14 N 3 NaO 3 S) solution using a high pressure mercury lamp as lamp-house. The relation of photocatalytic activity and silver content was studied in detail. It was found that silver content influences phase structure of TiO 2 thin films, and silver in the films is metallic Ag (Ag 0 ). With increasing silver content from 0 to 20 vol%, photocatalytic activity of the films increases first and then decreases. A suitable amount (2.5-5 vol%) silver addition can significantly enhance the photocatalytic activity of TiO 2 films. The enhanced photocatalytic activity was mainly attributed to the extension of visible light absorption region of the films, the presence of anatase phase, the increase of oxygen anion radicals 2 O − and reactive center of surface Ti 3+ , and the better separation between electrons and holes on the films surface.silver, nanoparticle, TiO 2 thin film, photocatalytic activity, RF magnetron sputtering, methyl orange Citation:Meng F M, Lu F, Sun Z Q, et al. A mechanism for enhanced photocatalytic activity of nano-size silver particle modified titanium dioxide thin films.

Effect of silver on the phase transition and wettability of titanium oxide films

“…Additionally, the lower chemical affinity of silver towards oxygen, as compared to titanium, also favours the reduction of silver to the metallic state during annealing, as it has been revealed by XPS and XRD analysis. Moreover, FESEM image analysis indicates that Ag atoms diffuse at higher annealing temperature and eventually nucleate forming large aggregates with lower surface energy, as observed by other authors 68 .…”

Plasmonic photocatalysis

“…For Ag-TiO 2 (i.e. Ag nanoparticles on TiO 2 film), a few studies reported similar enhanced photocatalytic and antimicrobial activities [179,203,204]. In Guillén-Santiago's work, Ag nanoparticles (90 and 200 nm) were deposited on TiO 2 thin films and enhanced the degradation of methylene blue under UV light [204].…”

Recent Developments in Environmental Photocatalytic Degradation of Organic Pollutants: The Case of Titanium Dioxide Nanoparticles—A Review

“…The defining property of a good semiconductor photocatalyst material is that the core element making up the material can reversibly change its valence state to accommodate a hole without decomposing the semiconductor (e.g., Ti 3+ → Ti 4+ in nonstoichiometric TiO 2 ) [8,18,91]. The photogenerated holes should be highly oxidizing to produce hydroxyl radicals ( • OH) and the photogenerated electrons should be reducing enough to produce superoxides from the oxygen [92].…”

“…even at low concentrations, but also to photocatalytically degrade and self-clean the contaminated environment [88,200,[219][220][221][222]. Moreover, the degradation of organic pollutants and reduction of metals to their zero oxidation states have been earmarked as one of the peak applications of TiO 2 for the treatment of river water, groundwater, the drainage water from fish-feeding tanks, and industrial wastewater [57,65,91,92,117,223,224]. Furthermore, photodegradation of organic pollutants by titanium dioxide results in the formation of innocuous products and therefore eliminates the problems associated with the recalcitrant DBPs [18,83,174,175,225].…”

“…As mentioned earlier, the tendency of titanium dioxide nanoparticles to aggregate and scatter incident light as well as the need for posttreatment recovery has made its largescale application economically impractical [91,211,264]. This had led to the exploration of a number of techniques to try and immobilise TiO 2 nanoparticles on solid supports not only to solve posttreatment problems but also to facilitate the renewable use of the catalyst [66].…”