Activity In Visible Light Region Research Articles

Synthesis of (Zn/Co)-based zeolite imidazole frameworks and their applications in visible light-driven photocatalytic degradation of Congo red

Zinc/cobalt (Zn/Co)-based zeolite imidazole frameworks (ZIFs) with varying Zn/Co molar ratios from 0/10 to 10/0 were synthesized by a microwave-assisted method, and the resulting materials were characterized by x-ray diffraction (XRD), nitrogen adsorption–desorption isotherms, scanning electron microscopy (SEM), x-ray photoelectron spectroscopy (XPS), and atomic absorption spectroscopy (AAS). The microwave-assisted approach required a very short synthesis time as well as yielded (Zn/Co)ZIFs with high specific surface areas (1637.3 m2 g−1). It was found that the introduction of zinc into ZIF-67 enhanced catalytic activity in visible-light region. (Zn/Co)ZIF with a Zn/Co molar ratio of 2/8 manifested an excellent photocatalytic degradation of Congo red (CGR). The kinetic model of photocatalytic degradation was proposed based on adsorption isotherms (Langmuir model) and a unimolecular reaction for the heterogeneous catalysis. Further, the reusability was also addressed.

Fe(III) modified BiOCl ultrathin nanosheet towards high-efficient visible-light photocatalyst

To pursue high photocatalytic activity in visible-light region, the Fe(III) modified BiOCl ultrathin nanosheet (Fe(III)@BOC NS) has been firstly synthesized via a facile solvothermal approach. The morphological and compositional characterizations reveal that the thickness of the as-prepared Fe(III)@BOC NS is less than 5 atomic layer with the exposure of active [001] facets. And the Fe(III) doping and surface grafting result in a 0.58eV down-shift of the BiOCl conduction band minimum extending the light absorption from ultraviolet light to visible light region, as well as a promoted interfacial charge transfer upon visible light irradiation. Meanwhile, the Fe(III) modification introduces unique active sites on the surface of ultrathin nanosheet facilitating the surface reaction. Moreover, both of the appropriate self-induced electric field of [001] facets, and the shortened charge carrier diffusion length of ultrathin nanosheet enhance the separation and transfer efficiency of charge carriers. Therefore, by taking those advantages, we experimentally demonstrate that the Fe(III)@BOC NS is a high-efficiency visible-light photocatalyst for both of environment remediation and water splitting.

C-doped mesoporous anatase TiO2 comprising 10 nm crystallites

We report a C-doped mesoporous anatase TiO2 with high surface area synthesized using multi-walled carbon nanotube (MWCNT) mat as a “rigid” template and carbon doping source. The characterization by SEM, HRTEM, X-ray diffraction and nitrogen adsorption revealed that TiO2 samples have a porous structure which are figuratively a inverse copy of MWCNT network and pore walls are formed by interconnected TiO2 nanoparticles with average diameter of ∼10nm. We found that annealing temperatures from 400 to 1000°C before MWCNT template removal had very limited effect on particle size (∼10nm), surface area (112–129m2/g) and total pore volume (0.74–0.85m2/g) of the samples through a significantly delayed phase transition from anatase to rutile started at 800°C, resulting in only ∼9.1% conversion at 1000°C. The pore size distribution is in mesopore range from 6 to 60nm peaked at ∼24nm. XPS analysis showed a relatively strong C1s peak at 288.4eV, indicating C doping at Ti sites, which is responsible for red shift of adsorption edge of UV–vis spectra and photocatalytic activity in visible-light region.

Highly active Fe2O3-doped TiO2 photocatalyst for degradation of trichloroethylene in air under UV and visible light irradiation: Experimental and computational studies

0.0–5.0wt% Fe2O3-doped TiO2 photocatalysts were synthesized by an ultrasonic-assisted co-precipitation method and used for degradation of 500ppm trichloroethylene (TCE) in air. The photocatalysts were treated at 100–400°C and characterized by high resolution transmission electron microscopy (HRTEM), powder X-ray diffraction (XRD), BET surface area, and Raman, UV–vis, and photoluminescence (PL) spectroscopies. For the samples treated at 100°C, XRD patterns show no significant peaks, while HRTEM micrographs indicate crystalline structures and diffraction patterns and Raman spectra reveal wide and weak peaks of anatase TiO2. As 0.1wt% Fe2O3 is added to TiO2, the surface area increases by a factor of 1.87 and reach to 448m2/g. UV–vis analyses indicate that, as the Fe2O3 content of the samples increases, the band gap energies decrease from 3.22eV for the pure TiO2 to 2.60eV for 5.0wt% Fe2O3-doped TiO2. Density functional theory simulations show that, when Fe3+ is doped into or FeO, Fe2O3 or Fe4O6 is adsorbed on anatase TiO2, the bad gap reduces and the iron oxide–TiO2 show photocatalytic activity in visible light region. The synthesized TiO2 showed about two times higher photocatalytic activity for TCE removal than that of Degussa P25. Moreover, 0.1wt% Fe2O3-doped TiO2 sample dried at 100°C showed a maximum photocatalytic TCE conversion of about 97% with minor amounts of CO as a hazardous byproduct. As the treatment temperature of the samples increase, the photocatalytic activity declines. Significant photocatalytic degradation of TCE was also observed for the Fe2O3-doped TiO2 samples, under visible light irradiation.

Enhanced visible light photocatalytic activity of TiO2 nanotube arrays modified with CdSe nanoparticles by electrodeposition method

Highly ordered TiO2 nanotube arrays (NTAs) were fabricated on titanium substrate via electrochemical anodization method. CdSe nanoparticles were deposited on the TiO2 NTAs through the electrodeposition process. The influence of electrolyte concentration and deposition time on the visible light photocatalytic performance of CdSe/TiO2 NTAs was studied systematically. The photocatalytic activity of as-prepared samples was evaluated by degradation of methyl orange under visible light irradiation. The results indicated that the CdSe nanoparticles distributed uniformly on the surface of TiO2 NTAs when deposited in the electrolyte containing 0.02M CdCl2, 2mM SeO2 and 0.02M Na2SO4 with time of 600s. After irradiation under visible light for 2h, the degradation rate of CdSe/TiO2 NTAs composite material reached 94.4%, while the degradation rate of unmodified TiO2 NTAs was only 6.2 % under the same condition, demonstrating that the CdSe/TiO2 NTAs exhibited higher photocatalytic activity in visible light region. In addition, a reasonable degradation rate of 80.96% was achieved even after being used for 5 times.

ZrO2/CeO2 nanocomposite: Two step synthesis, microstructure, and visible-light photocatalytic activity

ZrO2/CeO2 nanocomposite with photocatalytic activity in visible-light region was synthesized by calcination of the precursor prepared via a one-step hydrothermal method. The as-prepared composite includes ZrO2 nanoparticles assembled on the rough surface of CeO2 nanorods. CeO2 nanorods which have an average diameter of 500nm and lengths of 5–10μm were characterized to be the cubic structure, and ZrO2 nanoparticles with an average size of 300nm can be indexed as tetragonal and monoclinic structures. ZrO2/CeO2 composite photocatalyst exhibited photocatalytic activity under visible-light irradiation in the decomposition of rhodamine B (RhB) dye. Moreover, ZrO2/CeO2 nanocomposite showed an enhanced photocatalytic activity compared to the monocomponent ZrO2 and CeO2 nanocatalysts.

Photocatalytic activity of PANI loaded coordination polymer composite materials: Photoresponse region extension and quantum yields enhancement via the loading of PANI nanofibers on surface of coordination polymer

Abstract To enhance photocatalytic property of coordination polymer in visible light region, polyaniline (PANI) loaded coordination polymer photocatalyst was synthesized through in-situ chemical oxidation of aniline on the surface of coordination polymer. The photocatalytic activity of PANI loaded coordination polymer composite material for degradation of Rhodamine B (RhB) was investigated. Compared with pure coordination polymer photocatalyst, which can decompose RhB merely under UV light irradiation, PANI loaded coordination polymer photocatalyst displays more excellent photocatalytic activity in visible light region. Furthermore, PANI loaded coordination polymer photocatalyst exhibits outstanding stability during the degradation of RhB.

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Density functional calculations have been performed on the electronic structure of donor–acceptor (V–N, Nb–N, Cr–C and Mo–C) co-doped SrTiO3 to improve their photocatalytic activity in visible light region. By analyzing the electronic structure of pure and co-doped SrTiO3, we propose that the Mo–C co-doped system is promising materials for the visible light photocatalyst. It is found that the doping of Mo–C complex may shift the valence band edge up significantly, while keeping the conduction band edge almost unchanged. The calculated defect binding energies indicate that the co-doped systems are energetically favorable than their respective mono-doped systems.

Silver-modified TiO2 nanorods with enhanced photocatalytic activity in visible light region

Abstract Silver-modified TiO2 nanorods (SMTN) have been synthesized via controlled hydrolysis of tetrabutyltitanate (TBOT) in ethanol and immersion method by using AgNO3 as an Ag source. The physical and chemical properties of SMTN were studied by XRD, SEM, TEM, and UV–vis diffuse reflectance spectra (DRS). The photocatalytic activity of the as-prepared products was evaluated by photocatalytic decolorization of Rhodamine B (Rh B) aqueous solution at ambient temperature under visible light irradiation. The experimental results reveal that the TiO2 nanorods, which are well dispersed and uniform, attached large numbers of silver nanoparticles on the surface, and the major crystalline phase of TiO2 is anatase. The photocatalytic activity research shows that the SMTN exhibit an enhanced photocatalytic activity in visible light region compared with that of pure TiO2 nanorods and commercial TiO2 (P25).

First-principles study on strontium titanate for visible light photocatalysis

Density functional calculations have been performed on the electronic structure of donor–acceptor (V–N, Nb–N, Cr–C and Mo–C) co-doped SrTiO3 to improve their photocatalytic activity in visible light region. By analyzing the electronic structure of pure and co-doped SrTiO3, we propose that the Mo–C co-doped system is promising materials for the visible light photocatalyst. It is found that the doping of Mo–C complex may shift the valence band edge up significantly, while keeping the conduction band edge almost unchanged. The calculated defect binding energies indicate that the co-doped systems are energetically favorable than their respective mono-doped systems.

Synthesis of Sn<sup>4+</sup> Doped TiO<sub>2</sub> Nanotube and its Photocatalytic Activity

The PVP+Ti (OC4H9)4+SnCl4·5H2O/sesame oil composite fibers were successfully prepared by a sol-gel method combined with a coaxial electrospinning technique. The Sn4+/TiO2 nanotubes were obtained by calcining the above-mentioned composite fibers and characterized by XRD and TEM. XRD results show that increasing reaction temperature facilitates to form a stable phase. TEM results show that the Sn4+/TiO2 nanotubes have smooth surface with wall thickness of ~120 nm and are composed of small particles of ~5 nm. The photocatalytic activity of Sn4+/TiO2 nanotubes was investigated. The photodegradation efficiency of Sn4+/TiO2 nanotubes decreases in UV region but increases in visible light region. The photocatalytic properties of three 0.52at% Sn4+/TiO2 nanomaterials with different morphologies were also evaluated. The photodegradation efficiencies of Sn4+/TiO2 nanopowers, Sn4+/TiO2 nanofibers and Sn4+/TiO2 nanotubes increase in visible light region in sequence. In summary, chemical modification by doping Sn4+ and morphology changing for TiO2 can improve its photocatalytic activity in visible light region significantly.

Visible light photocatalysis of V2O5/TiO2 nanoheterostructures prepared via electrospinning

The V2O5/TiO2 nanoheterostructures with high photocatalytic activity in visible light region are synthesized via electrospinning directly. Photodecomposition rate of RhB by V2O5/TiO2 nanoheterostructures is much faster than that using of pure TiO2 nanofibers. Furthermore, the influence of V/Ti molar rate on visible light photocatalysis is studied. Experimental results indicate that optimum V/Ti molar rate of V2O5/TiO2 nanoheterostructures is found to be about 1:1. It can be attributed to the fewer efficient V2O5/TiO2 heterostructures formed in the V2O5/TiO2 nanofibers when the V/Ti molar rates deviate from 1:1. In addition, the V2O5/TiO2 nanoheterostructures show excellent photocatalytic stability after 10 cycles under visible light irradiation.

Tailoring the band gap of GaN codoped by VO for enhanced solar energy conversion from first-principles calculations

The electronic structure of a novel photocatalyst material designed in silico via co-doping of GaN by vanadium and oxygen has been investigated using the DFT + U method. The results show that this codoping approach leads to reduction of the band gap, along with significantly enhanced carrier mobility and photocatalytic activity in visible-light region, which is beneficial towards applications in solar energy conversion as well solar-assisted photocatalysis. Formation energies indicate that co-doping with anions is energetically favorable for cation mono-doping. Codoping by vanadium and oxygen in GaN shifts the Fermi level into the conduction band, resulting in increased carrier mobility and density.

Synthesis of Sn<sup>4+</sup> Doped TiO<sub>2</sub> Nano Powder and its Photocatalytic Activity

TiO2 nano powder doping with Sn4+ was directly synthesized by a low temperature hydrothermal method using tetrabutyl titanate (TBOT) as a Ti resource and NH4Cl as a dispersant. The synthesized nano powder was characterized by XRD, BET, TEM and EDS analyses. XRD results show that increasing reaction temperature facilitates to form a stable phase, and the synthesized nano power size is uniform with particle size of 10-20 nm. Doping Sn4+ ion does not result in an obvious lattice distortion. The effect of doping Sn4+ ion on photocatalytic activity in visible light region for modified TiO2 was investigated bydegrading methylene blue solution.

Rational Designs on TiO2-based Nanocomposites for Solar Photocatalytic Purification

ABSTRACTWe report an template-free process to fabricate S-C-codoped and (I2)n-C-codoped meso/nanoporous TiO2 nanocrystallites. Methylene blue solutions are used as a model pollute to evaluate the sorption and photocatalytic activity of the samples under visible light radiation. The high photocatalytic activity in visible light region of our samples is attributed to numerous oxygen vacancies, large specific surface area and the continuous states in the band gap of TiO2 introduced by I2 or S doping.

Effect of nitrogen-doping temperature on the structure and photocatalytic activity of the B,N-doped TiO 2

B,N-TiO 2 photocatalysts were synthesized by boron doping firstly and subsequently nitrogen doping in NH 3 at variable temperatures. The effects of the nitrogen doping temperature on the structure and photocatalytic activity of the B,N-codoped TiO 2 were investigated. The as-prepared samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), UV–vis diffuse reflectance spectrum (DRS), electron paramagnetic resonance (EPR) and X-ray photoelectron spectroscopy (XPS). The photocatalytic activity was evaluated with photocatalytic degradation of methyl orange dye (MO) under visible light and UV–visible light irradiation. The results suggested that the boron and nitrogen can be incorporated into the TiO 2 lattice either interstitially or substitutionally or both, while the Ti–O–B–N structure plays a vital role in photocatalytic activity in visible light region. The optimal nitrogen doping temperature is 550 °C. Higher temperature may form many oxygen vacancies and Ti 3+ species, resulting in the decrease of photocatalytic activity in visible light.