Improving the photocatalytic activity of TiO<sub>2</sub> through reduction

Zhang, Daoyu; Yang, Minnan; Dong, Shuai

doi:10.1039/c5ra05200a

Cited by 19 publications

(13 citation statements)

References 41 publications

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“…As a final remark, many other factors may have a deep influence on the behavior of TiO 2 regarding hydrogenation—the presence of surface and subsurface defects [94], the nature of the bulk phase [95], nanostructuring [96,97], interfacial water [98], or reduction [99]. More fundamental works to elucidate the structure of hydrogenated surfaces are needed to build a robust scenario for the complex behavior observed [100].…”

Section: Resultsmentioning

confidence: 99%

Understanding the Role of Rutile TiO2 Surface Orientation on Molecular Hydrogen Activation

2019

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Titanium oxide (TiO2) has been widely used in many fields, such as photocatalysis, photovoltaics, catalysis, and sensors, where its interaction with molecular H2 with TiO2 surface plays an important role. However, the activation of hydrogen over rutile TiO2 surfaces has not been systematically studied regarding the surface termination dependence. In this work, we use density functional theory (PBE+U) to identify the pathways for two processes: the heterolytic dissociation of H2 as a hydride–proton pair, and the subsequent H transfer from Ti to near O accompanied by reduction of the Ti sites. Four stoichiometric surface orientations were considered: (001), (100), (110), and (101). The lowest activation barriers are found for hydrogen dissociation on (001) and (110), with energies of 0.56 eV and 0.50 eV, respectively. The highest activation barriers are found on (100) and (101), with energies of 1.08 eV and 0.79 eV, respectively. For hydrogen transfer from Ti to near O, the activation barriers are higher (from 1.40 to 1.86 eV). Our results indicate that the dissociation step is kinetically more favorable than the H transfer process, although the latter is thermodynamically more favorable. We discuss the implications in the stability of the hydride–proton pair, and provide structures, electronic structure, vibrational analysis, and temperature effects to characterize the reactivity of the four TiO2 orientations.

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Section: Resultsmentioning

confidence: 99%

Understanding the Role of Rutile TiO2 Surface Orientation on Molecular Hydrogen Activation

2019

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“…TiO 2 samples containing oxygen vacancies were found to exhibit enhanced visible-light absorption, and photocatalytic activities. In the case of TiO 2 containing oxygen vacancies, a partially occupied impurity energy level ~2.0-2.5 eV above the valence band was experimentally observed [249][250][251][252]. The additional energy level has also been attributed to the existence of partially occupied Ti 3+ states, which create energy inter band gap energy levels just below the conduction band [253].…”

Section: Nonstoichiometric Tiomentioning

confidence: 99%

Visible-light activation of TiO2 photocatalysts: Advances in theory and experiments

Etacheri

Valentin

Schneider

et al. 2015

Journal of Photochemistry and Photobiology C: Photochemistry Re

1,176

549

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The remarkable achievement by Fujishima and Honda (1972) in the photoelectrochemical water splitting results in the extensive use of TiO 2 nanomaterials for environmental purification and energy storage/conversion applications. Though there are many advantages for the TiO 2 compared to other semiconductor photocatalysts, its band gap of 3.2 eV restrains application to the UV-region of the electromagnetic spectrum (λ ≤ 387.5 nm). As a result, development of visible-light active titanium dioxide is one of the key challenges in the field of semiconductor photocatalysis. In this review, advances in the strategies for the visible light activation, origin of visiblelight activity, and electronic structure of various visible-light active TiO 2 photocatalysts are discussed in detail. It has also been showed that if appropriate models are used, the theoretical insights can successfully be employed to develop novel catalysts to enhance the photocatalytic performance in the visible region. Recent developments in the theory and experiments in visible-light induced water splitting, degradation of environmental pollutants, water and air purification and antibacterial applications are also reviewed. Various strategies to identify appropriate dopants for improved visible-light absorption and electron-hole separation to enhance the photocatalytic activity are discussed in detail, and a number of recommendations are also presented.

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“…It was found that the valence band maximum (VBM) of TiO 2‐x was upshifted by the introduction of V o , which is consistent with previous reports. [ 47,48 ] As

{normalC}_{V_{o}}

increased, the VBM shifted more upward, and the conduction band minimum (CBM) was also upshifted, indicating a gradual shift in the band structures. Furthermore, V o ‐derived mid‐gap states were formed between the VBM and the CBM, and these deficient states led to a change in the bandgap, which is consistent with the EELS results (Figure 3c).…”

Section: Resultsmentioning

confidence: 99%

Continuous Oxygen Vacancy Gradient in TiO₂ Photoelectrodes by a Photoelectrochemical‐Driven “Self‐Purification” Process

Kim

Choi

Choung

et al. 2022

Advanced Energy Materials

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Oxygen vacancies have been treated as an important material engineering tool to enhance catalytic performance; for instance, oxygen vacancies suppress charge recombination at the Schottky interface, and thus, the photocurrent can be improved. In this regard, the gradient distribution of oxygen vacancies in n‐type metal oxides produces the ideal band structure for minimizing e−/h+ recombination by efficient hole extraction; however, its achievement remains a daunting challenge. Here, a photoelectrochemical (PEC)‐driven “self‐purification” process is suggested, which can effectively generate a gradient distribution of oxygen vacancies in the thickness range of ≈9.5 nm. As a result, a charge transport efficiency of >95% can be achieved by efficient hole migration from the photoanode to the electrolyte. This unique protocol is expected to provide an advanced metal oxide photocatalyst and photoelectrochemical electrode that exhibit superior photocatalytic performance with enhanced charge separation.

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Improving the photocatalytic activity of TiO₂ through reduction

Cited by 19 publications

References 41 publications

Understanding the Role of Rutile TiO2 Surface Orientation on Molecular Hydrogen Activation

Understanding the Role of Rutile TiO2 Surface Orientation on Molecular Hydrogen Activation

Visible-light activation of TiO2 photocatalysts: Advances in theory and experiments

Continuous Oxygen Vacancy Gradient in TiO₂ Photoelectrodes by a Photoelectrochemical‐Driven “Self‐Purification” Process

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Improving the photocatalytic activity of TiO2 through reduction

Cited by 19 publications

References 41 publications

Understanding the Role of Rutile TiO2 Surface Orientation on Molecular Hydrogen Activation

Understanding the Role of Rutile TiO2 Surface Orientation on Molecular Hydrogen Activation

Visible-light activation of TiO2 photocatalysts: Advances in theory and experiments

Continuous Oxygen Vacancy Gradient in TiO2 Photoelectrodes by a Photoelectrochemical‐Driven “Self‐Purification” Process

Contact Info

Product

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Improving the photocatalytic activity of TiO₂ through reduction

Continuous Oxygen Vacancy Gradient in TiO₂ Photoelectrodes by a Photoelectrochemical‐Driven “Self‐Purification” Process