Metal-promoted titania photocatalysis for destruction of nitrates and organics from aqueous environments

This review article provides an overview of activities in the rapidly developing field of water purification via photocatalytic methods and focuses on the removal of nitrate ions with simultaneous removal of the hole scavenger. Many of the issues associated with provision of potable water in the developing world may be resolved by the use of simple physical methodologies such as filtration. However, many of the issues associated with water purity in the developed world involve complex, stable molecules present at low concentrations that are nonetheless capable of producing toxic effects in plants and animals and that require more demanding removal technologies. Photocatalytic methods can be operated remotely and often show minimal production of undesired side products. Titania alone shows limitations, not only in terms of the slow rate of photoreduction of nitrate but also in terms of selectivity and the need to employ radiation in the UV region due to the magnitude of the band gap. Key challenges may be defined as: reducing the band gap/increasing absorption in the visible region, enhancing the adsorption capacity/access to the surface sites and reducing the rate of hole/electron recombination. The present article will focus on the use of titania-based materials that involve metal co-catalysts for nitrate reduction. This article is part of a discussion meeting issue ‘Providing sustainable catalytic solutions for a rapidly changing world’.

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Electronic, Structural, and Optical Structure of Mono-Doped and Co-Doped (210) TiO2 Brookite Surfaces for Application in Dye-Sensitized Solar Cells—A First Principles Study

Materials ◽

10.3390/ma14143918 ◽

2021 ◽

Vol 14 (14) ◽

pp. 3918

Author(s):

Ratshilumela S. Dima ◽

Lutendo Phuthu ◽

Nnditshedzeni E. Maluta ◽

Joseph K. Kirui ◽

Rapela R. Maphanga

Keyword(s):

Solar Cells ◽

Band Gap ◽

Dye Sensitized Solar Cells ◽

Visible Region ◽

Electromagnetic Spectrum ◽

Doped Tio2 ◽

Dye Sensitized ◽

Sensitized Solar Cells ◽

Co Doped ◽

Optical Structure

Titanium dioxide (TiO2) polymorphs have recently gained a lot of attention in dye-sensitized solar cells (DSSCs). The brookite polymorph, among other TiO2 polymorphs, is now becoming the focus of research in DSSC applications, despite the difficulties in obtaining it as a pure phase experimentally. The current theoretical study used different nonmetals (C, S and N) and (C-S, C-N and S-N) as dopants and co-dopants, respectively, to investigate the effects of mono-doping and co-doping on the electronic, structural, and optical structure properties of (210) TiO2 brookite surfaces, which is the most exposed surface of brookite. The results show that due to the narrowing of the band gap and the presence of impurity levels in the band gap, all mono-doped and co-doped TiO2 brookite (210) surfaces exhibit some redshift. In particular, the C-doped, and C-N co-doped TiO2 brookite (210) surfaces exhibit better absorption in the visible region of the electromagnetic spectrum in comparison to the pure, S-doped, N-doped, C-S co-doped and N-S co-doped TiO2 brookite (210) surfaces.

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Properties of Novel Non-Silicon Materials for Photovoltaic Applications: A First-Principle Insight

Materials ◽

10.3390/ma11102006 ◽

2018 ◽

Vol 11 (10) ◽

pp. 2006 ◽

Cited By ~ 3

Author(s):

Murugesan Rasukkannu ◽

Dhayalan Velauthapillai ◽

Federico Bianchini ◽

Ponniah Vajeeston

Keyword(s):

Band Gap ◽

Density Functional ◽

Crystalline Silicon ◽

Visible Region ◽

Initial Population ◽

First Principle ◽

Direct Band Gap ◽

Depth Analysis ◽

Photovoltaic Applications ◽

Direct Band

Due to the low absorption coefficients of crystalline silicon-based solar cells, researchers have focused on non-silicon semiconductors with direct band gaps for the development of novel photovoltaic devices. In this study, we use density functional theory to model the electronic structure of a large database of candidates to identify materials with ideal properties for photovoltaic applications. The first screening is operated at the GGA level to select only materials with a sufficiently small direct band gap. We extracted twenty-seven candidates from an initial population of thousands, exhibiting GGA band gap in the range 0.5–1 eV. More accurate calculations using a hybrid functional were performed on this subset. Based on this, we present a detailed first-principle investigation of the four optimal compounds, namely, TlBiS2, Ba3BiN, Ag2BaS2, and ZrSO. The direct band gap of these materials is between 1.1 and 2.26 eV. In the visible region, the absorption peaks that appear in the optical spectra for these compounds indicate high absorption intensity. Furthermore, we have investigated the structural and mechanical stability of these compounds and calculated electron effective masses. Based on in-depth analysis, we have identified TlBiS2, Ba3BiN, Ag2BaS2, and ZrSO as very promising candidates for photovoltaic applications.

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Effect of thickness on the optical properties of Gaas thin films

Journal of Bangladesh Academy of Sciences ◽

10.3329/jbas.v37i1.15684 ◽

2013 ◽

Vol 37 (1) ◽

pp. 83-91 ◽

Cited By ~ 13

Author(s):

Chitra Das ◽

Jahanara Begum ◽

Tahmina Begum ◽

Shamima Choudhury

Keyword(s):

Thin Films ◽

Dielectric Constant ◽

Refractive Index ◽

Band Gap ◽

Optical Band Gap ◽

Visible Region ◽

Solar Spectrum ◽

Band Gap Energy ◽

Optical Parameters ◽

Gap Energy

Effect of thickness on the optical and electrical properties of gallium arsenide (GaAs) thin films were studied. The films of different thicknesses were prepared by vacuum evaporation method (~10-4 Pa) on glass substrates at a substrate temperature of 323 K. The film thickness was measured in situ by a frequency shift of quartz crystal. The thicknesses were 250, 300 and 500 nm. Absorption spectrum of this thin film had been recorded using UV-VIS-NIR spectrophotometer in the photon wavelength range of 300 - 2500 nm. The values of some important optical parameters of the studied films (absorption coefficient, optical band gap energy and refractive index; extinction co-efficient and real and imaginary parts of dielectric constant) were determined using these spectra. Transmittance peak was observed in the visible region of the solar spectrum. Here transmittance showed better result when thicknesses were being increased. The optical band gap energy was decreased by the increase of thickness. The refractive index increased by increasing thickness while extinction co-efficient and real and imaginary part of dielectric constant decreased. DOI: http://dx.doi.org/10.3329/jbas.v37i1.15684 Journal of Bangladesh Academy of Sciences, Vol. 37, No. 1, 83-91, 2013

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Visible Electro- and Photoluminescence from Porous Silicon and its Related Optoelectronic Properties

MRS Proceedings ◽

10.1557/proc-256-219 ◽

1991 ◽

Vol 256 ◽

Cited By ~ 19

Author(s):

Nobuyoshi Koshida ◽

Hideki Koyama

Keyword(s):

Porous Silicon ◽

Optical Absorption ◽

Size Effect ◽

Band Gap ◽

Visible Region ◽

Optoelectronic Properties ◽

Porous Si ◽

Quantum Size ◽

Effect Model ◽

Injection Type

ABSTRACTThe optoelectronic properties of porous Si (PS) are presented in terms of electroluminescence (EL), photoluminescence (PL), photoconduction (PC), and optical absorption. Observations of injection-type EL, efficient PL, band-gap widening, and photosensitivities In the visible region are consistent with the quantum size effect model in PS.

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Preparation, characterization and enhanced photocatalytic activity of Ni2+ doped titania under solar light

Open Chemistry ◽

10.2478/s11532-009-0115-y ◽

2010 ◽

Vol 8 (1) ◽

pp. 142-148 ◽

Cited By ~ 22

Author(s):

L. Gomathi Devi ◽

Nagaraju Kottam ◽

S. Girish Kumar ◽

K. Eraiah Rajashekhar

Keyword(s):

Band Gap ◽

Anatase Phase ◽

Sol Gel ◽

Visible Region ◽

Analytical Techniques ◽

Red Shift ◽

Solar Light ◽

Spectral Studies ◽

Doped Titania ◽

Charge Carrier Trapping

AbstractAnatase TiO2 was prepared by sol-gel method through the hydrolysis of TiCl4. Ni2+ was doped into the TiO2 matrix in the concentration range of 0.02 to 0.1 at.% and characterized by various analytical techniques. Powder X-ray diffraction revealed only anatase phase for all the samples, while diffuse reflectance spectral studies indicated a red shift in the band gap absorption to the visible region. The photocatalytic activities of these photocatalysts were probed for the degradation of methyl orange under natural solar light. The photocatalyst with optimum doping of 0.08 at.% Ni2+, showed enhanced activity, which is attributed to: (i) effective separation of charge carriers and (ii) large red shift in the band gap to visible region. The influence of crystallite size and dopant concentration on the charge carrier trapping — recombination dynamics is investigated.

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Bandgap engineering of few-layered MoS2 with low concentrations of S vacancies

RSC Advances ◽

10.1039/d0ra01676d ◽

2020 ◽

Vol 10 (27) ◽

pp. 15702-15706 ◽

Cited By ~ 2

Author(s):

Wen He ◽

Jia Shi ◽

Hongkang Zhao ◽

Hui Wang ◽

Xinfeng Liu ◽

...

Keyword(s):

Band Gap ◽

Molybdenum Disulfide ◽

Bandgap Engineering ◽

Band Gap Engineering ◽

Low Concentrations ◽

Optoelectronic Applications ◽

Layered Mos2

Band-gap engineering of molybdenum disulfide (MoS2) by introducing vacancies is of particular interest owing to the potential optoelectronic applications.

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Effects in Band Gap for Photocatalysis in TiO2 Support by Adding Gold and Ruthenium

Processes ◽

10.3390/pr8091032 ◽

2020 ◽

Vol 8 (9) ◽

pp. 1032

Author(s):

Omar Ricardo Fonseca-Cervantes ◽

Alejandro Pérez-Larios ◽

Víctor Hugo Romero Arellano ◽

Belkis Sulbaran-Rangel ◽

Carlos Alberto Guzmán González

Keyword(s):

Beneficial Effect ◽

Band Gap ◽

Sol Gel ◽

Visible Region ◽

Ultra Violet ◽

Reduced Form ◽

Nano Catalyst ◽

Tio2 Support ◽

The Impact ◽

Insight Into

One of the key features of a nano catalyst for photocatalysis is the band gap, because, through its analysis, the potential of the catalyst can be determined. In this investigation, the impact on the band gap of different catalysts made by the sol–gel method, compared with TiO2 P25 Sigma-Aldrich, showing the effect of using gold or ruthenium as a metal supported on TiO2, with two different dosage percentages of 1 and 3 percent, was analysed. Additionally, two oxidation states of the catalyst, the reduced form and the oxidized form of the metal, were used to see the effect on the band gap. The experiments show that the gold addition has a higher beneficial effect on the band gap for the UV region (ultra violet region), and the ruthenium addition has a higher beneficial effect for the UV/visible region. The preferred oxidation state for the band gap was the oxidized state. The characterisation of the catalyst provided an insight into the relation between the band gap and the catalyst itself.

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Modulation of Three Dimensional Photonic Band Gap in Visible Region

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.31.20 ◽

2007 ◽

Vol 31 ◽

pp. 20-22 ◽

Cited By ~ 2

Author(s):

Y.P. Liu ◽

Y.P. Guo ◽

Z.J. Yan ◽

C.M. Huang ◽

Y.Y. Wang

Keyword(s):

Optical Properties ◽

Band Gap ◽

Photonic Band Gap ◽

Bragg Reflection ◽

Quartz Substrate ◽

Three Dimensional ◽

Visible Region ◽

Sphere Size ◽

Vertical Deposition Method ◽

Photonic Band

Three dimensional (3D) SiO2 photonic crystals films were fabricated on quartz substrate by vertical deposition method. The effects of various preparation parameters on optical properties were studied by optical transmission measurements. Bragg reflection on parallel sets of (111) planes were observed in all the samples. The center wavelength of [111] photonic band gap (PBG) varied from 450 nm to 680 nm with the increasing sphere size. For a given sphere size, the (111) Bragg reflection of as-deposited sample shifted towards lower wavelengths as the sintering temperature T increased. The role of evaporation temperature on the optical properties of the film was also investigated. The PBG can be correspondingly modulated in visible region by changing various preparation parameters.

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Dependence on the Partial Pressure of Oxygen on the Shift in the Energy Band-gap of CdO Thin Films in the Visible Region

Active and Passive Electronic Components ◽

10.1155/2001/37629 ◽

2001 ◽

Vol 24 (1) ◽

pp. 57-61 ◽

Cited By ~ 7

Author(s):

M. A. Grado-Caffaro ◽

M. Grado-Caffaro ◽

S. L. Sapienza

Keyword(s):

Thin Films ◽

Partial Pressure ◽

Band Gap ◽

Energy Band ◽

Visible Region ◽

Point Of View ◽

Theoretical Point ◽

Partial Pressure Of Oxygen ◽

Energy Band Gap ◽

Cdo Thin Films

In this paper, the dependence on the partial pressure of oxygen of the shift in the energy band-gap of CdO thin films for the visible region is investigated from the theoretical point of view on an experimental basis. In our analysis, the role played by the dependence of the carrier density upon the above pressure is emphasized.

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