Enhanced Photocatalytic Activity of Titania by Co-Doping with Mo and W

Avilés-García, Osmín; Valencia, Jaime Espino; Romero, Rubı́; Rico-Cerda, José Luis; Arroyo-Albiter, Manuel; Solís-Casados, Dora Alicia; Natividad, Reyna

doi:10.3390/catal8120631

Cited by 46 publications

(27 citation statements)

References 51 publications

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“…Such a presence of oxygen vacancies proves the existence of sub-stoichiometric metal oxides in our catalysts. It is worth commenting that Zr cation in ZrO 2 is energetically very difficult to reduce [31,32]. The charge state of zirconium is expected to be either 0 as in the case of metal, or +4 as in ZrO 2 .…”

Section: Resultsmentioning

confidence: 99%

Hydrogen Production from Aqueous Methanol Solutions Using Ti–Zr Mixed Oxides as Photocatalysts under UV Irradiation

et al. 2019

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The synthesis and characterisation of Ti–Zr mixed oxides containing 1 to 10 wt.% of Zr is herein reported. In addition, the samples were tested as photocatalysts in the generation of hydrogen from aqueous methanol solutions. The solids were prepared by sol-gel and then characterised by X-ray diffraction, high resolution electron microscopy, X-ray photoelectron spectroscopy, physisorption of nitrogen, scanning electron microscopy, UV-vis and Raman spectroscopies. The results show the presence of anatase as a predominant structure and the oxides present larger specific surface areas than that of pure titania. A maximum value of 168 m2/g was determined for the sample with 5 wt.% of zirconium. The calculated band gap energies varied from 3.05 to 3.15 eV. It was observed that the greater the zirconium content in the solid, the higher the generation rate of hydrogen when testing the Ti–Zr solids as photocatalysts. Under our experimental conditions, the best catalyst, Ti–Zr oxide with 10 wt. % Zr, showed a production rate of 2100 μmol of H2/h which was about tenfold higher than that observed for pure titania.

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Section: Resultsmentioning

confidence: 99%

Hydrogen Production from Aqueous Methanol Solutions Using Ti–Zr Mixed Oxides as Photocatalysts under UV Irradiation

et al. 2019

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“…The significant Raman bands associated with rutile are noted around 439.26 cm −1 and 602.94 cm −1 , respectively. As compared to pure anatase, the E g peaks of Mo-TiO 2 are red shifted with an increase of line width [71]. The peak shift is explained by a number of competitive mechanisms, such as phonon confinement, lattice strain/ distortion and non-stoichiometric defects due to oxygen vacancies [72][73][74][75].…”

Section: Raman Spectramentioning

confidence: 95%

Mo doped TiO₂: impact on oxygen vacancies, anatase phase stability and photocatalytic activity

et al. 2020

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This work outlines an experimental and theoretical investigation of the effect of molybdenum (Mo) doping on the oxygen vacancy formation and photocatalytic activity of TiO 2 . Analytical techniques such as x-ray diffraction (XRD), Raman, x-ray photoelectron spectroscopy (XPS) and photoluminescence (PL) were used to probe the anatase to rutile transition (ART), surface features and optical characteristics of Mo doped TiO 2 (Mo-TiO 2 ). XRD results showed that the ART was effectively impeded by 2 mol% Mo doping up to 750°C, producing 67% anatase and 33% rutile. Moreover, the crystal growth of TiO 2 was affected by Mo doping via its interaction with oxygen vacancies and the Ti-O bond. The formation of Ti-O-Mo and Mo-Ti-O bonds were confirmed by XPS results. Phonon confinement, lattice strain and non-stoichiometric defects were validated through the Raman analysis. DFT results showed that, after substitutional doping of Mo at a Ti site in anatase, the Mo oxidation state is Mo 6+ and empty Mo-s states emerge at the titania conduction band minimum. The empty Mo-d states overlap the anatase conduction band in the DOS plot. A large energy cost, comparable to that computed for pristine anatase, is required to reduce Mo-TiO 2 through oxygen vacancy formation. Mo 5+ and Ti 3+ are present after the oxygen vacancy formation and occupied states due to these reduced cations emerge in the energy gap of the titania host. PL studies revealed that the electron-hole recombination process in Mo-TiO 2 was exceptionally lower than that of TiO 2 anatase and rutile. This was ascribed to introduction of 5s gap states below the CB of TiO 2 by the Mo dopant. Moreover, the photo-generated charge carriers could easily be trapped and localised on the TiO 2 surface by Mo 6+ and Mo 5+ ions to improve the photocatalytic activity. coatings [8,9]. The most commonly existing crystalline polymorphs of TiO 2 are anatase, rutile and brookite [10][11][12]. Anatase is accepted to be the more active phase of TiO 2 and is preferred by the ceramic industries to fabricate light active antimicrobial indoor building materials such as ceramics, glass, tiles and sanitary surfaces [13,14]. This requires thermal stability of the anatase phase under typical ceramic processing conditions. TiO 2 anatase is mainly fabricated at low calcination temperatures (∼500°C) to prevent the anatase to rutile phase transition (ART) [15][16][17], which produces the less photo-active rutile phase. The photo-activity of anatase arises from its appropriate band edge positions, electron affinity, ionisation potential, and the long lifetime of charge carriers [10,12,18]. Moreover, transient photo-conductance analysis has revealed that the electron-hole recombination phenomena in anatase (101) phase is much slower compared to rutile (110), which is credited in part to the indirect band gap of anatase [11,19].The unit cells of anatase and rutile phases are composed of TiO 6 octahedra with titanium atoms at the centre and oxygen atoms at the vertices [20]. Both anatase and rutile have a t...

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“…Apart from Ti 3+ ions, other transition metals, such as copper (Cu), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe) and nickel (Ni), are typically employed to enhance the visible-light photocatalytic activity of titania [88][89][90][91][92][93][94][95][109][110][111][112][113][114][115]. The redshift effectiveness takes the following order: V > Cr > Mn > Fe > Ni [86].…”

Section: Metal Dopingmentioning

confidence: 99%

“…This is typically termed the 'co-doping'. The enhancement in the photocatalytic activity of co-doped TiO 2 is attributed to the synergistic effect of the dopants in increasing visible light absorption, thus facilitating electron-hole generation and suppressing the recombination rate [90,[113][114][115]. Very recently, Aviles-Garcia et al synthesized W and Mo co-doped TiO 2 , and reported that the nanocomposite with the W:Mo = 1:1 ratio having a bandgap of 2.87 eV exhibits a synergistic effect between the dopants to generate more hydroxyl radicals for degrading 4-chlorophenol.…”

Section: Metal Dopingmentioning

confidence: 99%

Visible-Light Active Titanium Dioxide Nanomaterials with Bactericidal Properties

2020

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This article provides an overview of current research into the development, synthesis, photocatalytic bacterial activity, biocompatibility and cytotoxic properties of various visible-light active titanium dioxide (TiO2) nanoparticles (NPs) and their nanocomposites. To achieve antibacterial inactivation under visible light, TiO2 NPs are doped with metal and non-metal elements, modified with carbonaceous nanomaterials, and coupled with other metal oxide semiconductors. Transition metals introduce a localized d-electron state just below the conduction band of TiO2 NPs, thereby narrowing the bandgap and causing a red shift of the optical absorption edge into the visible region. Silver nanoparticles of doped TiO2 NPs experience surface plasmon resonance under visible light excitation, leading to the injection of hot electrons into the conduction band of TiO2 NPs to generate reactive oxygen species (ROS) for bacterial killing. The modification of TiO2 NPs with carbon nanotubes and graphene sheets also achieve the efficient creation of ROS under visible light irradiation. Furthermore, titanium-based alloy implants in orthopedics with enhanced antibacterial activity and biocompatibility can be achieved by forming a surface layer of Ag-doped titania nanotubes. By incorporating TiO2 NPs and Cu-doped TiO2 NPs into chitosan or the textile matrix, the resulting polymer nanocomposites exhibit excellent antimicrobial properties that can have applications as fruit/food wrapping films, self-cleaning fabrics, medical scaffolds and wound dressings. Considering the possible use of visible-light active TiO2 nanomaterials for various applications, their toxicity impact on the environment and public health is also addressed.

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Enhanced Photocatalytic Activity of Titania by Co-Doping with Mo and W

Cited by 46 publications

References 51 publications

Hydrogen Production from Aqueous Methanol Solutions Using Ti–Zr Mixed Oxides as Photocatalysts under UV Irradiation

Hydrogen Production from Aqueous Methanol Solutions Using Ti–Zr Mixed Oxides as Photocatalysts under UV Irradiation

Mo doped TiO₂: impact on oxygen vacancies, anatase phase stability and photocatalytic activity

Visible-Light Active Titanium Dioxide Nanomaterials with Bactericidal Properties

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Enhanced Photocatalytic Activity of Titania by Co-Doping with Mo and W

Cited by 46 publications

References 51 publications

Hydrogen Production from Aqueous Methanol Solutions Using Ti–Zr Mixed Oxides as Photocatalysts under UV Irradiation

Hydrogen Production from Aqueous Methanol Solutions Using Ti–Zr Mixed Oxides as Photocatalysts under UV Irradiation

Mo doped TiO2: impact on oxygen vacancies, anatase phase stability and photocatalytic activity

Visible-Light Active Titanium Dioxide Nanomaterials with Bactericidal Properties

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Mo doped TiO₂: impact on oxygen vacancies, anatase phase stability and photocatalytic activity