Band gap engineering of nanotubular Fe2O3-TiO2 photoanodes by wet impregnation

Sołtys-Mróz, Monika; Syrek, Karolina; Pierzchała, Joanna; Wiercigroch, Ewelina

doi:10.1016/j.apsusc.2020.146195

Cited by 48 publications

(28 citation statements)

References 62 publications

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“…The position shift of such peaks can be due to a substitution reaction at/near the nanotube's surface during calcination. In this sense, the incorporation of Fe 3+ would increase the crystal radius and shift the Bragg angle, as explained by M. Sołtys-Mróz et al, 2020 [21]. Finally, in the Mott-Schottky plot, a shift of the EFB toward negative potentials indicates a change in the surface of the nt-TiO2 and charge transfer processes across the material, as discussed elsewhere [21].…”

Section: Hematite Deposition Onto Anodized Tio2 Nanotube Arraysmentioning

confidence: 79%

“…The electrochemical characterization (using Electrochemical Impedance Spectroscopy) was performed from −0.8 to 0.2 V, with an amplitude of 5 mV, 1000 Hz using NaOH (1 M). The graphs presented correspond to a Mott-Schottky treatment, as usually reported for semiconductors to evaluate the E FB [21]. On the other hand, the morphological study was done using a field emission scanning electron microscope (FE-SEM, FEI Quanta 250).…”

Section: Methodsmentioning

confidence: 99%

“…In this sense, Figure 2 shows the results obtained for the deposition of hematite using three different methods. In the following sections, a detailed characterization will be performed for each synthetic route to determine the better-suited modification of nt-TiO2 considering the high variability already reported regarding the impregnation method [21].…”

Section: Hematite Deposition Onto Anodized Tio2 Nanotube Arraysmentioning

confidence: 99%

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Comparison of Different Synthetic Routes of Hybrid Hematite-TiO2 Nanotubes-Based Electrodes

et al. 2021

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Nowadays, green hydrogen is an important niche of interest in which the search for a suitable composite material is indispensable. In this sense, titanium oxide nanotubes (TiO2 nanotube, TNTs) were prepared from double anodic oxidation of Ti foil in ethylene glycol electrolyte. The morphology of the nanotubes was characterized by scanning electron microscopy (SEM) and X-ray diffraction (XRD). Once characterized, nanotubes were used as templates for the deposition of hematite. The use of three synthetic procedures was assayed: Chemical Vapor Deposition (CVD), Successive Ionic Layer Adsorption and Reaction (SILAR), and electrochemical synthesis. In the first case, CVD, the deposition of hematite onto TiO2 yielded an uncovered substrate with the oxide and a negative shift of the flat band potential. On the other hand, the SILAR method yielded a considerable amount of hematite on the surface of nanotubes, leading to an obstruction of the tubes in most cases. Finally, with the electrochemical synthesis, the composite material obtained showed great control of the deposition, including the inner surface of the TNT. In addition, the impedance characterization showed a negative shift, indicating the changes of the interface electrode–electrolyte due to the modification with hematite. Finally, the screening of the methods showed the electrochemical synthesis as the best protocol for the desired material.

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Section: Hematite Deposition Onto Anodized Tio2 Nanotube Arraysmentioning

confidence: 79%

Section: Methodsmentioning

confidence: 99%

Section: Hematite Deposition Onto Anodized Tio2 Nanotube Arraysmentioning

confidence: 99%

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Comparison of Different Synthetic Routes of Hybrid Hematite-TiO2 Nanotubes-Based Electrodes

et al. 2021

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“…Another study of laser processing of TiO 2 -NTs has shown that, if the laser annealing is carried out in vacuum [39], it leads to the positive shift of the E FB , but it leads to the negative if the process was performed in water. On the other hand, it is known that the presence of hematite on the surface of TiO 2 -NTs [79], as well as their doping by Fe, leads to the negative shift of the E FB [80,81]. Taking into account the variation of E FB as a laser fluence function (Figure 12), it should be concluded that the iron incorporation into the TiO 2 structure is responsible for the E FB negative shift.…”

Section: Resultsmentioning

confidence: 96%

The Effect of Laser Re-Solidification on Microstructure and Photo-Electrochemical Properties of Fe-Decorated TiO2 Nanotubes

et al. 2020

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Fossil fuels became increasingly unpleasant energy source due to their negative impact on the environment; thus, attractiveness of renewable, and especially solar energy, is growing worldwide. Among others, the research is focused on smart combination of simple compounds towards formation of the photoactive materials. Following that, our work concerns the optimized manipulation of laser light coupled with the iron sputtering to transform titania that is mostly UV-active, as well as exhibiting poor oxygen evolution reaction to the material responding to solar light, and that can be further used in water splitting process. The preparation route of the material was based on anodization providing well organized system of nanotubes, while magnetron sputtering ensures formation of thin iron films. The last step covering pulsed laser treatment of 355 nm wavelength significantly changes the material morphology and structure, inducing partial melting and formation of oxygen vacancies in the elementary cell. Depending on the applied fluence, anatase, rutile, and hematite phases were recognized in the final product. The formation of a re-solidified layer on the surface of the nanotubes, in which thickness depends on the laser fluence, was shown by microstructure studies. Although a drastic decrement of light absorption was recorded especially in UV range, laser-annealed samples have shown activity under visible light even 20 times higher than bare titania. Electrochemical analysis has shown that the improvement of photoresponse originates mainly from over an order of magnitude higher charge carrier density as revealed by Mott-Schottky analysis. The results show that intense laser light can modulate the semiconductor properties significantly and can be considered as a promising tool towards activation of initially inactive material for the visible light harvesting.

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“…The nanostructures of the aerogel samples were investigated with a Field Emission Scanning Electron Microscope (FESEM) [51,52]. Scanning electron microscopy operating at electron energies below 5 keV is usually termed Low Voltage Scanning Electron Microscopy (LVSEM) [53].…”

Section: Low Voltage Scanning Electron Microscopy (Lvsem)mentioning

confidence: 99%

False Morphology of Aerogels Caused by Gold Coating for SEM Imaging

et al. 2021

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The imaging of non-conducting materials by scanning electron microscopy (SEM) is most often performed after depositing few nanometers thick conductive layers on the samples. It is shown in this work, that even a 5 nm thick sputtered gold layer can dramatically alter the morphology and the surface structure of many different types of aerogels. Silica, polyimide, polyamide, calcium-alginate and cellulose aerogels were imaged in their pristine forms and after gold sputtering utilizing low voltage scanning electron microscopy (LVSEM) in order to reduce charging effects. The morphological features seen in the SEM images of the pristine samples are in excellent agreement with the structural parameters of the aerogels measured by nitrogen adsorption-desorption porosimetry. In contrast, the morphologies of the sputter coated samples are significantly distorted and feature nanostructured gold. These findings point out that extra care should be taken in order to ensure that gold sputtering does not cause morphological artifacts. Otherwise, the application of low voltage scanning electron microscopy even yields high resolution images of pristine non-conducting aerogels.

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Band gap engineering of nanotubular Fe2O3-TiO2 photoanodes by wet impregnation

Cited by 48 publications

References 62 publications

Comparison of Different Synthetic Routes of Hybrid Hematite-TiO2 Nanotubes-Based Electrodes

Comparison of Different Synthetic Routes of Hybrid Hematite-TiO2 Nanotubes-Based Electrodes

The Effect of Laser Re-Solidification on Microstructure and Photo-Electrochemical Properties of Fe-Decorated TiO2 Nanotubes

False Morphology of Aerogels Caused by Gold Coating for SEM Imaging

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