Hydrogen activation at TiO2 anatase nanocrystals

Berger, Thomas; Diwald, Oliver; Knözinger, Erich; Napoli, F.; Chiesa, Mario; Giamello, Elio

doi:10.1016/j.chemphys.2007.06.021

Cited by 52 publications

(61 citation statements)

References 60 publications

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“…The same process, when the matrix is the reducible titanium dioxide, ends, as shown by Berger et al, 39 with ionization of the H atom and injection of an electron into the solid with formation of Ti 3+40…”

Section: Introductionmentioning

confidence: 72%

Mechanism of the Photoactivity under Visible Light of N-Doped Titanium Dioxide. Charge Carriers Migration in Irradiated N-TiO₂ Investigated by Electron Paramagnetic Resonance.

et al. 2012

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The generation of surface charge carriers in N-doped TiO 2 under various types of irradiation has been investigated by electron paramagnetic resonance using an approach consisting in scavenging surface migrated electrons and holes using oxygen and hydrogen, respectively. N-doped TiO 2 , which is moderately active in photocatalytic processes under visible light, forms surface electrons and, at lower extent, surface holes due to the synergistic effect of visible components (around 400 nm) and near-infrared ones. The visible radiation excites electrons from intra band gap NO x− states to the conduction band, while NIR frequencies excite electrons from the valence band to the NO x− centers. The limited concentration of such centers explains the moderate efficiency of the whole process and, consequently, of the photocatalytic activity of N-TiO 2 in visible light with respect to the case of UV light irradiation. Despite the mentioned limits this material remains a fundamental starting point for a new generation of photocatalytic systems exploiting solar light.

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Section: Introductionmentioning

confidence: 72%

Mechanism of the Photoactivity under Visible Light of N-Doped Titanium Dioxide. Charge Carriers Migration in Irradiated N-TiO₂ Investigated by Electron Paramagnetic Resonance.

et al. 2012

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“…The relatively high degree of stability of the Nb doped support may be attributed to the differences of the electronic conductivities associated with the different materials. Both Nb doped and reduced TiO 2 have higher electronic conductivity than the air calcined TiO 2 due to the presence of Ti 3+ species [14,27,28]. The TiO 2 material reduced in H 2 has the highest conductivity among the ceramic materials tested in this work.…”

Section: Electrochemical Measurementsmentioning

confidence: 79%

“…Thus, a certain fraction of Ti 3+ species is present in the TiO 2 lattice [14]. Another approach to improving the conductivity is the introduction of dopants, such as Nb or Ta, which have a higher valence state than Ti 4+ [4,15].…”

Section: Introductionmentioning

confidence: 99%

Pt nanoparticles deposited on TiO2 based nanofibers: Electrochemical stability and oxygen reduction activity

Bauer

Lee

Song

et al. 2010

Journal of Power Sources

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This article appeared in a journal published by Elsevier. The attached copy is furnished to the author for internal non-commercial research and education use, including for instruction at the authors institution and sharing with colleagues.Other uses, including reproduction and distribution, or selling or licensing copies, or posting to personal, institutional or third party websites are prohibited. The electrochemical stability of Pt deposited on TiO 2 based nanofibers was compared with commercially available carbon supported Pt. Prior to the Pt deposition the TiO 2 material, which was either undoped or Nb doped, was air calcined. In one case the undoped TiO 2 was also reduced in a hydrogen atmosphere. XRD analysis revealed that the unreduced TiO 2 was present in the anatase phase, irrespective of whether the Nb dopant was present, whereas the rutile phase was formed due to reduction with H 2 . The diameter of the TiO 2 fibers varied from 50 to 100 nm, and the average Pt particle diameter was approximately 5 nm. Pt supported on TiO 2 was more stable than Pt supported on C when subjected to 1000 voltammetric cycles in the range of 0.05-1.3 V vs. RHE. Nb doped TiO 2 showed the highest stability, retaining 60% of the electrochemically active surface area after 1000 cycles compared to the state after 100 cycles, whereas the carbon supported catalyst retained 20% of the active surface area. The commercial catalyst had the highest oxygen reduction activity due to its larger specific area (17.1 m 2 g −1 vs. 5.0 m 2 g −1 for Pt/TiO 2 -Nb, measured after 100 cycles) and the higher support conductivity. The Pt supported on Nb doped or on H 2 reduced TiO 2 was more active than Pt supported on air calcined and otherwise unmodified TiO 2 .Crown

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“…In this case, UV photons induce charge separation and the photo-formed hole, once migrated to the surface, reacts with molecular hydrogen (homolytic splitting) to give an hydroxyl group and an H atom which, in turn, ionizes injecting an electron in the solid. [38] Figure 3 compares the EPR spectrum of rutile obtained upon the described procedure (equations 3-5, Fig. 3(b)) with that recorded after the mild thermal annealing at 373K (Fig.s 2(a) and 3(a)).…”

Section: Electrons Injection In -Rutile Via Atomic Hydrogenmentioning

confidence: 99%

Nature of Reduced States in Titanium Dioxide as Monitored by Electron Paramagnetic Resonance. II: Rutile and Brookite Cases

et al. 2014

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Abstract.We have systematically used Electron Paramagnetic Resonance (EPR) to understand the nature of excess electron centers in Titanium dioxide and to classify their spectroscopic features. Excess electrons in TiO 2 (probably the most important photoactive oxide) have been generated either by photoinduced charge separation or by reductive treatments and are stabilized in the solid by titanium ions which reduce to paramagnetic Ti 3+ . These are monitored by EPR and classified on the basis of their g tensor values in order to amend a certain confusion present in the literature about this subject. In the previous paper of this series (S. Livraghi et al. J. Phys. Chem. C 2011, 115, 25413) excess electron centers in anatase were investigated while the present one is devoted to rutile and brookite, the two other TiO 2 polymorphs, in the aim of providing a thorough and consistent guideline to researchers working in the wide area of titanium dioxide applications.2

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Hydrogen activation at TiO2 anatase nanocrystals

Cited by 52 publications

References 60 publications

Mechanism of the Photoactivity under Visible Light of N-Doped Titanium Dioxide. Charge Carriers Migration in Irradiated N-TiO₂ Investigated by Electron Paramagnetic Resonance.

Mechanism of the Photoactivity under Visible Light of N-Doped Titanium Dioxide. Charge Carriers Migration in Irradiated N-TiO₂ Investigated by Electron Paramagnetic Resonance.

Pt nanoparticles deposited on TiO2 based nanofibers: Electrochemical stability and oxygen reduction activity

Nature of Reduced States in Titanium Dioxide as Monitored by Electron Paramagnetic Resonance. II: Rutile and Brookite Cases

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Hydrogen activation at TiO2 anatase nanocrystals

Cited by 52 publications

References 60 publications

Mechanism of the Photoactivity under Visible Light of N-Doped Titanium Dioxide. Charge Carriers Migration in Irradiated N-TiO2 Investigated by Electron Paramagnetic Resonance.

Mechanism of the Photoactivity under Visible Light of N-Doped Titanium Dioxide. Charge Carriers Migration in Irradiated N-TiO2 Investigated by Electron Paramagnetic Resonance.

Pt nanoparticles deposited on TiO2 based nanofibers: Electrochemical stability and oxygen reduction activity

Nature of Reduced States in Titanium Dioxide as Monitored by Electron Paramagnetic Resonance. II: Rutile and Brookite Cases

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Mechanism of the Photoactivity under Visible Light of N-Doped Titanium Dioxide. Charge Carriers Migration in Irradiated N-TiO₂ Investigated by Electron Paramagnetic Resonance.

Mechanism of the Photoactivity under Visible Light of N-Doped Titanium Dioxide. Charge Carriers Migration in Irradiated N-TiO₂ Investigated by Electron Paramagnetic Resonance.