Utilization Efficiency Of Visible Light Research Articles

Facile fabrication of mesoporosity driven N–TiO2@CS nanocomposites with enhanced visible light photocatalytic activity

For the efficient utilization of visible light from solar light illumination, wormhole mesoporous N-doped TiO2 modified with carbon and sulfur (abbreviated as N–TiO2@CS nanocomposites) have been fabricated using a sol–gel auto-combustion method. The prepared samples under different calcination temperatures were thoroughly characterized by XRD, TEM, FTIR, BET Surface area, UV-Vis DRS, XPS and PL. It has been demonstrated that in N–TiO2@CS nanocomposites, incorporated N in the crystal lattice of TiO2 exist as N–Ti–O, sulfur exist as sulfate ions (S6+) on the TiO2 surface and carbon species were modified on the surface of the photocatalyst. N-doping narrows the band gap and sulfate species on the surface of TiO2 act as co-catalyst. Moreover, the presence of surface carbon species enhances visible light harvesting and stimulates to separate photo generated charge carriers, which makes the system more potential towards photocatalytic application. The photocatalytic activities of the as prepared catalyst were evaluated for phenol degradation under visible light irradiation. The higher photocatalytic activity of the N–TiO2@CS nanocomposite calcined at 400 °C (STU400) is attributed to the synergistic combination of C, N and S atoms, the wormhole mesoporous frame with high surface area and high crystalline anatase phase of TiO2. The overall photocatalytic activity and the proposed mechanism are further confirmed through PL spectra and trapping of hydroxyl radicals.

Doping mode, band structure and photocatalytic mechanism of B–N-codoped TiO 2

The photocatalyst B and N codoped TiO 2 (B–N-TiO 2) was prepared via the sol–gel method by using boric acid and ammonia as B and N precursors. The doping mode, band structure and photocatalytic mechanism of B–N-TiO 2 were investigated well and elucidated in detail. B–N-TiO 2 showed the narrowed band gap and thus extended the optical absorption due to interstitial N and [NOB] species in the TiO 2 crystal lattice. The coexistence of interstitial N and [NOB] species in the TiO 2 crystal lattice and surface NO x species allowed the more efficient utilization of visible light. Simultaneously, interstitial [NOB] and N species and surface B 2O 3 and NO x species facilitated the separation of photo generated electrons and holes and suppress their recombination effectively. Hence, B–N-TiO 2 showed a higher photocatalytic activity than pure TiO 2, N-doped TiO 2 (N-TiO 2) and B-doped TiO 2 (B-TiO 2) under both UV and visible light irradiation.

Nitrogen and Lanthanum Co-Doped TiO<sub>2</sub> with Enhanced Photocatalytic Activity

Nitrogen and lanthanum co-doped nanocsystalline titania photocatalysts were prepared by a homogeneous precipitation-hydrothermal process. The photocatalytic activity of the prepared samples on photodegradation of rhodamine B in visible light irradiation was studied. The nitrogen and lanthanum co-doping could greatly improve the photocatalytic activity of titania in visible light irradiation, probablely due to a synergistic effect of co-doping. The nitrogen doping could narrow the band gap of titania and enhance the utilization efficiency of visible light, while the lanthanum doping could accelerate the separation of photo-generated electrons and holes. Furthermore, the lanthanum doping could increase the adsorption of organic pollutants on the surface of photocatalyst.

A visible light-responsive iodine-doped titanium dioxide nanosphere

I-doped titanium dioxide nanospheres (I-TNSs) were synthesized via a two-step hydrothermal synthesis route, their potential for the efficient utilization of visible light was evaluated. The prepared anatase-phase I-TNSs had a bimodal porous size distribution with a Brunauer-Emmett-Teller surface area of 76 m 2/g, a crystallite size of approximately 14 nm calculated from X-ray diffraction data, and a remarkable absorption in the visible light region at wavelengths > 400 nm. The photocatalytic activity of the samples was evaluated by decoloration of Methyl Orange in aqueous solution under visible light irradiation in comparison to the iodine-doped TiO 2 (I-TiO 2). The I-TNSs showed higher photocatalytic efficiency compared with I-TiO 2 after irradiation for 180 min even though the latter had a much greater surface area (115 m 2/g). It was concluded that the surface area was not the predominant factor determining photocatalytic activity, and that the good crystallization and bimodal porous nanosphere structure were favourable for photocatalysis.

Improving the thermal stability and photocatalytic activity of nanosized titanium dioxide via La3+ and N co-doping

The microstructure and properties of nitrogen and lanthanum co-doped nanocrystalline titania photocatalysts have been studied. The catalyst samples were prepared in a homogeneous precipitation–hydrothermal process and characterized by XRD, XPS, UV–DRS and BET analyses. The results indicated that the nitrogen and La3+ doping could inhibit the phase transformation and crystallite growth of TiO2 and enhance the thermal stability of TiO2 structure. In addition, the experiment results showed that the thermal stability of TiO2 increased with the increasing of La3+ doping. The photocatalytic activities of samples for photodegradation of rhodamine B under visible light irradiation using different La3+ doping contents were also studied. There were optimal values of La3+ doping content for the La3+ doped and nitrogen/La3+ co-doped TiO2 corresponding the highest photodegradation percentages. The nitrogen and La3+ co-doped titania could greatly improve the photocatalytic activity in visible light irradiation, whose probable mechanism is a synergistic effect of co-doping. The nitrogen doping could narrow the band gap of titania and enhance the utilization efficiency of visible light, while the La3+ doping could accelerate the separation of photo-generated electrons and holes. Furthermore, the La3+ doping could increase the adsorption of organic pollutants on the surface of photocatalyst.

Efficient utilization of visible light in the photoreduction of chloroaromatic compounds

Photocatalytic reduction of chloroaromatics to the corresponding aromatic compounds has been accomplished using visible dyes in the presence of amines. An electron transfer mechanism is implicated by the experimental results, with the formation of an aryl chloride radical anion being the key step leading to dechlorination.