Selective synthesis of N-doped mesoporous TiO2 phases having enhanced photocatalytic activity

In the absence of a dopant or precursor modification, anatase to rutile transformation in synthetic TiO 2 usually occurs at a temperature of 600 ºC to 700 ºC. Conventionally, metal oxide dopants (e.g. Al 2 O 3 and SiO 2 ) are used to tune the anatase to rutile transformation. A simple methodology is reported here to extend the anatase rutile transformation by employing various concentrations of urea.XRD and Raman spectroscopy were used to characterize various phases formed during thermal treatment. A significantly higher anatase phase (97%) has been obtained at 800 ºC using a 1:1 (Ti (OPr) 4 : urea) composition and 11% anatase composition is retained even after calcining the powder at 900 ºC. On comparison a sample which has been prepared without urea showed that rutile phases started to form at a temperature as low as 600 °C. The effect of smaller amounts of urea such as 1:0.25 and 1:0.5 (Ti (OPr) 4 :urea) has also been studied and compared. The investigation concluded that the stoichiometric modification by urea 1:1 (Ti (OPr) 4 :urea) composition is most effective in extending the anatase to rutile phase transformation by 200 ºC compared to the unmodified samples. In addition, BET analysis carried out on samples calcined at 500 °C showed that the addition of urea up to 1:1 (Ti (OPr) 4 :urea) increased the total pore volume (from 0.108 cm 3 /g to 0.224 cm 3 /g) and average pore diameter (11 nm to 30 nm) compared to the standard sample. Samples prepared using 1:1 (Ti (OPr) 4 :urea) composition calcined at 900 ºC show significantly higher photocatalytic activity compared to the standard sample prepared under similar conditions. Kinetic analysis shows a marked increase in the photocatalytic degradation of rhodamine 6G on going from the standard sample (0.016 min , decoloration in 50 mins).

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“…48 It has also been reported that a mixture of anatase and rutile is more photoactive than 100% anatase.…”

Section: -49mentioning

confidence: 98%

Synthesis of High-Temperature Stable Anatase TiO₂ Photocatalyst

et al. 2007

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“…The basic idea of this previous consideration is that the induction rate (10) defined from the induction time measurements also defines the initial aggregation kinetics, which can be expressed as dm 2 /dt p dI/dt (13) where I is the light intensity scattered by the colloids. As our results show (see Fig.…”

Section: F Reaction Kinetics Involving Hyumentioning

confidence: 99%

“…Different methods were applied to the N-TiO 2 fabrication: laser pyrolysis, 2 pulsed-laser deposition, 3 electrophoretic deposition, 4 plasma treatment, 5 annealing under gas atmosphere, [6][7][8] hydrothermal, 9 solvothermal, 10 mechanochemical, 11 spray pyrolysis, 12 wet 13,14 and sol-gel [15][16][17][18] methods, with addition of nitrogen-containing precursors (e.g. urea, ammonia) followed by calcination.…”

Section: Introductionmentioning

confidence: 99%

TiO2 doping by hydroxyurea at the nucleation stage: towards a new photocatalyst in the visible spectral range

Azouani¹,

Tieng²,

Chhor³

et al. 2010

Phys. Chem. Chem. Phys.

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We report an original method of preparation of OCN-doped TiO 2 for photocatalysis in the visible spectral range. The preparation is achieved by a sol-gel route using titanium tetraisopropoxide precursor. Special attention was paid to fluid micromixing, which enables homogeneous reaction conditions in the reactor bulk and monodispersity of the produced clusters/nanoparticles. The dopant hydroxyurea (HyU, CH 4 N 2 O 2 ) is injected into the reactive fluid at the nucleation stage, which lasts tens of milliseconds. The doping results in a strong yellow coloration of the nanocolloids due to the absorption band in the spectral range 380-550 nm and accelerates the aggregation kinetics of both nuclei at the induction stage and sub-nuclei units (clusters) at the nucleation stage. FTIR, Raman and UV-visible absorption analyses show the formation of a stable HyU-TiO 2 complex. EXAFS spectra indicate no appreciable changes of the first-shell Ti atom environment. The doping agent takes available surface sites of TiO 2 clusters/ nanoparticles attaining B10% molar loading. The reaction kinetics then accelerates due to a longer collisional lifetime between nanoparticles induced by the formation of a weak QOÁ Á ÁTi bond. The OCN-group bonding to titanium atoms produces a weakening of the CQO double bond and a strengthening of the C-N and N-O bonds.

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“…Urea is a common source of nitrogen for doping in mp-TiO 2 since it is readily available and easy to introduce into TiO 2 precursor sol or solid TiO 2 using a urea solution [22,56,[180][181][182][183][184][185][186][187][188][189]. In addition to being a nitrogen source, urea can contribute to forming mesopores in titania by generation of CO 2 gas bubbles during its decomposition (Equation (6)) [22,183].…”

Section: Ureamentioning

confidence: 99%

Synthesis and Catalytic Applications of Non-Metal Doped Mesoporous Titania

et al. 2017

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Mesoporous titania (mp-TiO 2 ) has drawn tremendous attention for a diverse set of applications due to its high surface area, interfacial structure, and tunable combination of pore size, pore orientation, wall thickness, and pore connectivity. Its pore structure facilitates rapid diffusion of reactants and charge carriers to the photocatalytically active interface of TiO 2 . However, because the large band gap of TiO 2 limits its ability to utilize visible light, non-metal doping has been extensively studied to tune the energy levels of TiO 2 . While first-principles calculations support the efficacy of this approach, it is challenging to efficiently introduce active non-metal dopants into the lattice of TiO 2 . This review surveys recent advances in the preparation of mp-TiO 2 and their doping with non-metal atoms. Different doping strategies and dopant sources are discussed. Further, co-doping with combinations of non-metal dopants are discussed as strategies to reduce the band gap, improve photogenerated charge separation, and enhance visible light absorption. The improvements resulting from each doping strategy are discussed in light of potential changes in mesoporous architecture, dopant composition and chemical state, extent of band gap reduction, and improvement in photocatalytic activities. Finally, potential applications of non-metal-doped mp-TiO 2 are explored in water splitting, CO 2 reduction, and environmental remediation with visible light.

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Selective synthesis of N-doped mesoporous TiO2 phases having enhanced photocatalytic activity

Cited by 56 publications

References 28 publications

Synthesis of High-Temperature Stable Anatase TiO₂ Photocatalyst

Synthesis of High-Temperature Stable Anatase TiO₂ Photocatalyst

TiO2 doping by hydroxyurea at the nucleation stage: towards a new photocatalyst in the visible spectral range

Synthesis and Catalytic Applications of Non-Metal Doped Mesoporous Titania

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Selective synthesis of N-doped mesoporous TiO2 phases having enhanced photocatalytic activity

Cited by 56 publications

References 28 publications

Synthesis of High-Temperature Stable Anatase TiO2 Photocatalyst

Synthesis of High-Temperature Stable Anatase TiO2 Photocatalyst

TiO2 doping by hydroxyurea at the nucleation stage: towards a new photocatalyst in the visible spectral range

Synthesis and Catalytic Applications of Non-Metal Doped Mesoporous Titania

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Synthesis of High-Temperature Stable Anatase TiO₂ Photocatalyst

Synthesis of High-Temperature Stable Anatase TiO₂ Photocatalyst