Influence of Ti3+ defect-type on heterogeneous photocatalytic H2 evolution activity of TiO2

Mohajernia, Shiva; Andrýsková, Pavlína; Zoppellaro, Giorgio; Hejazi, Seyedsina; Kment, Štěpán; Zbořil, Radek; Schmidt, Jochen; Schmuki, Patrik

doi:10.1039/c9ta10855f

Cited by 98 publications

(97 citation statements)

References 30 publications

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“…A JEOL JES‐X‐320 EPR was used for recording EPR spectra according to a previously published approach. [ 49 ]…”

Section: Methodsmentioning

confidence: 99%

“…Several works [ 25,46–48 ] show that annealing TiO 2 in H 2 or Ar/H 2 mainly leads to two types of defect centers that is, Ti 3+ centers located in regular lattice positions and surface exposed Ti 3+[ 25,46–48 ] . The density of these defects on the TiO 2 surface can be adjusted by the annealing conditions (namely by the annealing atmosphere and the temperature [ 49,50 ] )—this is also illustrated in Figure S1, Supporting Information. The defects can be distinguished and characterized most effectively by EPR spectroscopy where regular lattice positions provide a typical signal with a g value of ≈1.99 and surface exposed Ti 3+ show a signal with a characteristic g value of ≈1.93.…”

Section: Figurementioning

confidence: 99%

“…XPS results for the Ar treated samples show much lower Pt concentrations (0.06, 0.09, and 0.14 at% of Pt for samples annealed at 300, 400, and 500 °C) in comparison with the Ar/H 2 treated samples (see Figure S9, Supporting Information). This difference is mainly due to formation of defects with different nature upon annealing in different environments [ 49 ] . Ar atmosphere leads to formation of Ti 3+ centers that have mainly the nature of regular lattice position defects [ 49 ] .…”

Section: Figurementioning

confidence: 99%

“…This difference is mainly due to formation of defects with different nature upon annealing in different environments [ 49 ] . Ar atmosphere leads to formation of Ti 3+ centers that have mainly the nature of regular lattice position defects [ 49 ] .…”

Section: Figurementioning

confidence: 99%

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On the Controlled Loading of Single Platinum Atoms as a Co‐Catalyst on TiO₂ Anatase for Optimized Photocatalytic H₂ Generation

et al. 2020

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The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/adma.201908505.Single-atom (SA) catalysis is a novel frontline in the catalysis field due to the often drastically enhanced specific activity and selectivity of many catalytic reactions. Here, an atomic-scale defect engineering approach to form and control traps for platinum SA sites as co-catalyst for photocatalytic H 2 generation is described. Thin sputtered TiO 2 layers are used as a model photocatalyst, and compared to the more frequently used (001) anatase sheets. To form stable SA platinum, the TiO 2 layers are reduced in Ar/H 2 under different conditions (leading to different but defined Ti 3+ -O v surface defects), followed by immersion in a dilute hexachloroplatinic acid solution. HAADF-STEM results show that only on the thin-film substrate can the density of SA sites be successfully controlled by the degree of reduction by annealing. An optimized SA-Pt decoration can enhance the normalized photocatalytic activity of a TiO 2 sputtered sample by 150 times in comparison to a conventional platinum-nanoparticle-decorated TiO 2 surface. HAADF-STEM, XPS, and EPR investigation jointly confirm the atomic nature of the decorated Pt on TiO 2 . Importantly, the density of the relevant surface exposed defect centers-thus the density of Pt-SA sites, which play the key role in photocatalytic activity-can be precisely optimized.Single-atom (SA) or single-site catalysis (SACs) has over the past years become an increasingly fascinating topic in the catalysis field. [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15] SACs have allowed new approaches in heterogeneous catalysis, [12,13] minimized the use of precious metals, [14]

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“…A JEOL JES‐X‐320 EPR was used for recording EPR spectra according to a previously published approach. [ 49 ]…”

Section: Methodsmentioning

confidence: 99%

Section: Figurementioning

confidence: 99%

Section: Figurementioning

confidence: 99%

Section: Figurementioning

confidence: 99%

See 2 more Smart Citations

On the Controlled Loading of Single Platinum Atoms as a Co‐Catalyst on TiO₂ Anatase for Optimized Photocatalytic H₂ Generation

et al. 2020

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“…While several studies have carried out photoelectrochemical studies of reduced (hydrogenated) TiO2 nanomaterials, very limited knowledge on detailed photoelectrochemical behaviour of differently reduced TiO2 nanotubes has been accumulated so far. Therefore, in this work we perform thermal reduction of anodic TNTAs in pure H2 atmosphere at different temperatures (leading to different defect structures [23]) and systematically study their subsequent photoelectrochemical properties by IPCE spectroscopy, transient photocurrent measurements, IMPS, PEIS, and Mott-Schottky analysis.…”

Section: Introductionmentioning

confidence: 99%

Photoelectrochemical properties of “increasingly dark” TiO2 nanotube arrays

Denisov

Qin

Cha

et al. 2020

Journal of Electroanalytical Chemistry

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Black" TiO2 nanotube arrays (TNTAs) of different darkness are formed by thermal reduction of anodic TiO2 nanotube layers in H2 atmosphere at different temperatures (300-500°C), and their (photo-)electrochemical properties are studied by IPCE spectroscopy, transient photocurrent measurements, IMPS, PEIS, and Mott-Schottky analysis. Hydrogenation of the TNTAs leads to the enhancement of their IPCE (by up to 1.5 times), despite increased recombination losses at anodic potentials. Reduced TNTAs demonstrate a "metallic" behavior by a characteristic frequency response of their impedance and phase angle, reduced charge transfer resistance at anodic bias, increased double layer capacitance, and remarkably increased donor densities (up to 7.25 × 10 23 cm-3). The observed alterations in the properties of TNTAs after hydrogenation are ascribed to the formation of defects and TiHx.

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Advanced Photocatalysts: Pinning Single Atom Co‐Catalysts on Titania Nanotubes

Zhou

Hwang

Tomanec

et al. 2021

Adv Funct Materials

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Single atom (SA) catalysis, over the last 10 years, has become a forefront in heterogeneous catalysis, electrocatalysis, and most recently also in photocatalysis. Most crucial when engineering a SA catalyst/support system is the creation of defined anchoring points on the support surface to stabilize reactive SA sites. Here, a so far unexplored but evidently very effective approach to trap and stabilize SAs on a broadly used photocatalyst platform is introduced. In self-organized anodic TiO 2 nanotubes, a high degree of stress is incorporated in the amorphous oxide during nanotube growth. During crystallization (by thermal annealing), this leads to a high density of Ti 3+ -O v surface defects that are hardly present in other common titania nanostructures (as nanoparticles). These defects are highly effective for SA iridium trapping. Thus a SA-Ir photocatalyst with a higher photocatalytic activity than for any classic co-catalyst arrangement on the semiconductive substrate is obtained. Hence, a tool for SA trapping on titania-based back-contacted platforms is provided for wide application in electrochemistry and photoelectrochemistry. Moreover, it is shown that stably trapped SAs provide virtually all photocatalytic reactivity, with turnover frequencies in the order of 4 × 10 6 h −1 in spite of representing only a small fraction of the initially loaded SAs.

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Influence of Ti³⁺ defect-type on heterogeneous photocatalytic H₂ evolution activity of TiO₂

Abstract: Surface exposed Ti3+ and lattice embedded Ti3+ in an optimum ratio is the determining factor for optimized photocatalytic H2 evolution.

Cited by 98 publications

References 30 publications

On the Controlled Loading of Single Platinum Atoms as a Co‐Catalyst on TiO₂ Anatase for Optimized Photocatalytic H₂ Generation

On the Controlled Loading of Single Platinum Atoms as a Co‐Catalyst on TiO₂ Anatase for Optimized Photocatalytic H₂ Generation

Photoelectrochemical properties of “increasingly dark” TiO2 nanotube arrays

Advanced Photocatalysts: Pinning Single Atom Co‐Catalysts on Titania Nanotubes

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Influence of Ti3+ defect-type on heterogeneous photocatalytic H2 evolution activity of TiO2

Abstract: Surface exposed Ti3+ and lattice embedded Ti3+ in an optimum ratio is the determining factor for optimized photocatalytic H2 evolution.

Cited by 98 publications

References 30 publications

On the Controlled Loading of Single Platinum Atoms as a Co‐Catalyst on TiO2 Anatase for Optimized Photocatalytic H2 Generation

On the Controlled Loading of Single Platinum Atoms as a Co‐Catalyst on TiO2 Anatase for Optimized Photocatalytic H2 Generation

Photoelectrochemical properties of “increasingly dark” TiO2 nanotube arrays

Advanced Photocatalysts: Pinning Single Atom Co‐Catalysts on Titania Nanotubes

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Product

Resources

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Influence of Ti³⁺ defect-type on heterogeneous photocatalytic H₂ evolution activity of TiO₂

On the Controlled Loading of Single Platinum Atoms as a Co‐Catalyst on TiO₂ Anatase for Optimized Photocatalytic H₂ Generation

On the Controlled Loading of Single Platinum Atoms as a Co‐Catalyst on TiO₂ Anatase for Optimized Photocatalytic H₂ Generation