Highly efficient photoelectrochemical and photocatalytic anodic TiO2 nanotube layers with additional TiO2 coating

Sopha, Hanna; Krbal, Miloš; Ng, Siowwoon; Přikryl, Jan; Zazpe, Raúl; Yam, F.K.; Macák, Jan M.

doi:10.1016/j.apmt.2017.06.002

Cited by 83 publications

(60 citation statements)

References 50 publications

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“…In order to provide an additional proof of MoSe x O y successful coatings, the energy‐dispersive X‐ray spectroscopy (EDX) elemental mapping and line scan of the 50 cycles MoSe x O y ‐coated TiO 2 nanotube layer taken from the interface of the bottom part of the TiO 2 nanotube layer and the underlying Ti substrate is shown in Figures S1 and S2 (Supporting Information). Similar uniform and ultrathin coatings within TiO 2 nanotube layers were also observed in our previous works for various secondary materials, including Al 2 O 3 , TiO 2 , ZnO, and CdS . By measuring the thickness of the MoSe x O y shown in Figure a,b, we estimate that the thickness of the 50 cycles MoSe x O y coating is ≈10 nm.…”

Section: Resultssupporting

confidence: 87%

“…It is well known that the photocatalytic conversion rates can be further enhanced by an external potential, as shown in the literature . In these cases, the applied potential contributes to the pronounced separation of photogenerated electrons and holes.…”

Section: Resultsmentioning

confidence: 94%

“…The TiO 2 nanotube walls, in fact, consist of numerous electron traps, associated with under‐coordinated Ti 4+ sites and oxygen vacancies . Prolonged photoresponse time up to tens of seconds by MoSe 2 /TiO 2 heterostructure was seen by Lei et al However, with the adequate MoSe x O y coatings within TiO 2 nanotube layers, the fast and reversible responses indicate that the coatings passivate the surface defect states on the TiO 2 nanotube walls, hence improve the charge carriers separation and increase the recombination lifetime for high quantum efficiency, which is in line with our previous reports . From the photocurrent transient curves in Figure b, the passivation effect can be noticed even for 5 cycles coating (≈1 nm), which has shown considerable photocurrent enhancement compared to the blank nanotube layer.…”

Section: Resultsmentioning

confidence: 99%

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MoSe_xO_y‐Coated 1D TiO₂ Nanotube Layers: Efficient Interface for Light‐Driven Applications

Krbal

Zazpe

et al. 2017

Adv Materials Inter

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in the materials science community. [2] Apart from the generation of H 2 and O 2 gases, photocatalysis can be extended to other applications. The early works on the irradiation of TiO 2 for purification of water via photocatalytic decomposition of pollutants were demonstrated by Frank and Bard in late 1970s. [3][4][5] These initial works and many reports later have shown that photooxidation of inorganic and organic contaminants is a promising route for environmental remediation. [6][7][8][9][10][11][12] In fact, the key factors that determine the efficiencies of a photocatalyst include its light harvesting capability and reduced charge carriers recombination of the photo generated electron-hole pairs. [3,13] However, TiO 2 possesses rather wide bandgap energies between 3.0 and 3.2 eV, with high photo activity only in the UV region (λ ≤ 390 nm) equivalent to only ≈5% of the solar spectrum. [14,15] Nevertheless, owing to its nontoxicity, low-cost synthesis, chemical inertness, and resistance against photocorrosion, TiO 2 has been long studied and recognized as the most promising photocatalyst material. [13,16] In order to harness more from the abundant renewable energy source, that is, solar energy, tremendous efforts have been devoted to reduce the bandgap energy of TiO 2 and broaden its optical absorption to the visible region. [8,[13][14][15]17,18] Bandgap engineering has been extensively carried out Ultrathin molybdenum oxyselenide (MoSe x O y ) coatings are made first ever by atomic layer deposition (ALD) within anodic 1D TiO 2 nanotube layers for photoelectrochemical and photocatalytic applications. The coating thickness is controlled through varying ALD cycles from 5 to 50 cycles (corresponding to ≈1-10 nm). In the ultraviolet region, the coatings have enhanced up to four times the incident photon-to-current conversion efficiency (IPCE), and the highest IPCE is recorded at 32% at (at λ = 365 nm). The coatings notably extend the photoresponse to the visible spectral region and remarkable improvement of photocurrent densities up to ≈40 times is registered at λ = 470 nm. As a result, the MoSe x O y -coated-TiO 2 nanotube layers have shown to be an effective photocatalyst for methylene blue degradation, and the optimal performance is credited to a coating thickness between 2 and 5 nm (feasible only by ALD). The enhancement in photoactivities of the presented heterojunction is mainly associated with the passivation effect of MoSe x O y on the TiO 2 nanotube walls and the suitability of bandgap position between MoSe x O y and TiO 2 interface for an efficient charge transfer. In addition, MoSe x O y possesses a narrow bandgap, which favors the photoactivity in the visible spectral region.

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Section: Resultssupporting

confidence: 87%

Section: Resultsmentioning

confidence: 94%

Section: Resultsmentioning

confidence: 99%

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MoSe_xO_y‐Coated 1D TiO₂ Nanotube Layers: Efficient Interface for Light‐Driven Applications

Krbal

Zazpe

et al. 2017

Adv Materials Inter

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“…The peculiar characteristics are particularly helpful for the deposition of a secondary material in high aspect ratio structures, such as porous anodic alumina, and TiO 2 nanotube layers, as in this study. Very recently, a few works have shown the potential of ALD secondary material in TiO 2 nanostructures . These include ALD ZnO loaded TiO 2 nanowires and nanotubes, both focused on the photocatalytic and photoelectrochemcial (PEC) applications .…”

Section: Introductionmentioning

confidence: 99%

ZnO Coated Anodic 1D TiO₂ Nanotube Layers: Efficient Photo‐Electrochemical and Gas Sensing Heterojunction

Kuberský

Krbal

et al. 2017

Adv Eng Mater

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The authors demonstrate, in this work, a fascinating synergism of a high surface area heterojunction between TiO 2 in the form of ordered 1D anodic nanotube layers of a high aspect ratio and ZnO coatings of different thicknesses, produced by atomic layer deposition. The ZnO coatings effectively passivate the defects within the TiO 2 nanotube walls and significantly improve their charge carrier separation. Upon the ultraviolet and visible light irradiation, with an increase of the ZnO coating thickness from 0.19 to 19 nm and an increase of the external potential from 0.4-2 V, yields up to 8-fold enhancement of the photocurrent density. This enhancement translates into extremely high incident photon to current conversion efficiency of %95%, which is among the highest values reported in the literature for TiO 2 based nanostructures. In addition, the photoactive region is expanded to a broader range close to the visible spectral region, compared to the uncoated nanotube layers. Synergistic effect arising from ZnO coated TiO 2 nanotube layers also yields an improved ethanol sensing response, almost 11-fold compared to the uncoated nanotube layers. The design of the high-area 1D heterojunction, presented here, opens pathways for the light-and gas-assisted applications in photocatalysis, water splitting, sensors, and so on.

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“…The effective utilization of ALD for deposition of various materials within TiO 2 nanotube layers has been demonstrated e.g. for oxides [26][27][28][29][30] and sulfides [31,32], yielding interesting synergic effects. Even though the use of the ALD to deposit Pt nanoparticles on various catalytic supports has been reported in previous works [33][34][35], no reports show an effective deposition of Pt nanoparticles within high aspect ratio 1D TiO 2 tubular nanostuctures.…”

Section: Introductionmentioning

confidence: 99%

Uniform ALD deposition of Pt nanoparticles within 1D anodic TiO2 nanotubes for photocatalytic H2 generation

Yoo

Zazpe

Cha

et al. 2018

Electrochemistry Communications

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In the present work we investigate the utilization of Pt nanoparticles produced by atomic layer deposition (ALD) within anodic TiO 2 nanotube (NT) layers for photocatalytic H 2 production. By varying numbers of ALD cycles, Pt nanoparticles with different diameters, uniformly decorating the tube walls were produced. The Pt nanoparticle size (2-15 nm), the Pt mass loading and areal density were strongly dependent on the number of Pt ALD cycles. The deposited Pt nanoparticles turned out to be highly effective as co-catalyst for photocatalytic H 2 generation. A most effective performance for solar light photocatalysis was reached after 26 ALD cycles (yielding an optimal areal coverage with particles of a diameter ≈ 7 nm). For UV light optimum photocatalytic efficiency was reached after 40 ALD cycles.

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Highly efficient photoelectrochemical and photocatalytic anodic TiO2 nanotube layers with additional TiO2 coating

Cited by 83 publications

References 50 publications

MoSe_xO_y‐Coated 1D TiO₂ Nanotube Layers: Efficient Interface for Light‐Driven Applications

MoSe_xO_y‐Coated 1D TiO₂ Nanotube Layers: Efficient Interface for Light‐Driven Applications

ZnO Coated Anodic 1D TiO₂ Nanotube Layers: Efficient Photo‐Electrochemical and Gas Sensing Heterojunction

Uniform ALD deposition of Pt nanoparticles within 1D anodic TiO2 nanotubes for photocatalytic H2 generation

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Highly efficient photoelectrochemical and photocatalytic anodic TiO2 nanotube layers with additional TiO2 coating

Cited by 83 publications

References 50 publications

MoSexOy‐Coated 1D TiO2 Nanotube Layers: Efficient Interface for Light‐Driven Applications

MoSexOy‐Coated 1D TiO2 Nanotube Layers: Efficient Interface for Light‐Driven Applications

ZnO Coated Anodic 1D TiO2 Nanotube Layers: Efficient Photo‐Electrochemical and Gas Sensing Heterojunction

Uniform ALD deposition of Pt nanoparticles within 1D anodic TiO2 nanotubes for photocatalytic H2 generation

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MoSe_xO_y‐Coated 1D TiO₂ Nanotube Layers: Efficient Interface for Light‐Driven Applications

MoSe_xO_y‐Coated 1D TiO₂ Nanotube Layers: Efficient Interface for Light‐Driven Applications

ZnO Coated Anodic 1D TiO₂ Nanotube Layers: Efficient Photo‐Electrochemical and Gas Sensing Heterojunction