Photocatalytic Activity of Titanium Dioxide Modified by Silver Nanoparticles

Abstract

Photocatalytic activity of Ag/TiO(2) composites obtained by photoreduction treatment (PRT) was investigated. The composite materials, containing various ratio of silver nanoparticles (0.6-3.7 wt %) were obtained by depositing silver on the Evonic-Degussa P25 titania surface. Selected samples whose color varied between light rose and purple brown were examined by SEM, TEM, XPS, DRS, and BET techniques. Flat band potential was determined using Roy method. TEM analysis showed spherically shaped silver nanoparticles of the diameter 4-12 nm. The XPS measurements revealed that silver particles were obtained mainly in metallic form. DRS spectra and photovoltage measurements showed that silver nanoparticles modified the P25 spectral properties but they changed neither the band gap nor the location of flat band potential. The photocatalytic activity of Ag/P25 composite was compared to the photocatalytic activity of pure P25 in the photooxidation reaction of an important potable water contaminant humic acid (HA) and two model compounds, oxalic acid (OxA) and formic acid (FA). The photodecomposition reaction was investigated in a batch reactor containing aqueous suspension of a photocatalyst illuminated by either UV or artificial sunlight (halogen lamp). The tests proved that a small amount of silver nanoparticles deposited on the titania surface triggers the increase in photocatalytic activity; this increase depends, however, on the decomposed substance.

Photocatalytic Water Treatment by Titanium Dioxide: Recent Updates

“…In all reports, except in silver doping, the visible light photocatalytic activity was mainly attributed to the associated red shift that originated from the creation of local bands between the VB and CB of NTO (Figure 4). Silver doping in P25 by a photoreduction method did not reduce the band gap of the doped catalyst, but superior photocatalytic degradation of oxalic acid was still observed, when compared to un-doped P25, under artificial sunlight [125]. This was explained by the formation of silver oxalate, which absorbed from the visible region and was subsequently degraded.…”

“…Doping NTO with metals and non-metals creates new energy levels between the VB and CB of TiO 2 [121], which in turn reduces its band gap and helps the doped catalyst to absorb in the visible region (Figure 4). Recently, researchers have reported the successful doping of vanadium [122], iron [123], rhodium [50], palladium [124], and silver [125] metals, and carbon [105,126], nitrogen [51,96,105,121,124,127,128], sulfur [98,129], fluorine [96], and iodine [130] non-metals in NTO to achieve the visible light photocatalytic degradation of various chemicals and Escherichia coli in aqueous solution (Table 3). In all reports, except in silver doping, the visible light photocatalytic activity was mainly attributed to the associated red shift that originated from the creation of local bands between the VB and CB of NTO (Figure 4).…”

N-doped TiO2 Synthesised via Microwave Induced Photocatalytic on RR4 dye Removal under LED Light Irradiation

“…The modification of TiO 2 photocatalyst towards visible active catalyst is has been tremendously exploited since 1972 where the first discovery of TiO 2 on it capability to produce hydroxyl radical under activation of UV light (Hashimoto et al 2005). Some researchers made a modification of TiO 2 by using the doping technique with metal and nonmetal element (Kuo et al 2011;Wodka et al 2010;Yu et al 2014). Some researchers claimed that doping with metal may decrease the band gap energy.…”

Photocatalytic Activity of Vis-Responsive Ag-Nanoparticles/TiO2 Composite Thin Films Fabricated by Molecular Precursor Method (MPM)

“…These noble metals act separately or simultaneously depending on the photoreaction conditions, experimental methods used and they may (i) enhance the electron-hole separation by acting as electron traps [8][9][10][11], (ii) extend the light absorption into the visible range and enhance surface electron excitation by sizeand shape-dependent plasmon resonances excited by visible light [7,[12][13][14] and/or (iii) modify the surface properties of TiO 2 [15,16]. The early methods [17][18][19], to produce noble-metal nanoparticles are still used today and continue to be the standard by which other synthesis methods are compared [20][21][22].…”