Stable anatase TiO<sub>2</sub> formed by calcination of rice-like titania nanorod at 800 °C exhibits high photocatalytic activity

Grover, Inderpreet Singh; Singh, Satnam; Pal, Bonamali

doi:10.1039/c4ra01850h

Cited by 13 publications

(7 citation statements)

References 27 publications

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“…The optical properties of the translucent ECrGO/TiO 2 photoelectrodes were analyzed by UV-Vis spectroscopy in transmittance mode ( Figure S4, Supplementary data). A Taucplot representation of the acquired spectra is shown in Figure 2, The TiO 2 electrode reveals an absorption peak at 3.9 eV, and an absorption edge at 3.20 eV, ( Figure 2) in agreement with the literature value for the indirect bandgap of TiO 2 [36]. In ECrGO/TiO 2 electrodes, both the absorption peak and the edge shift to lower energies with respect to the blank TiO 2 electrode.…”

Section: Photoelectrochemical Measurementssupporting

confidence: 86%

Photoactivity improvement of TiO2 electrodes by thin hole transport layers of reduced graphene oxide

Hernández‐Ferrer

Ansón‐Casaos

Víctor-Román

et al. 2019

Electrochimica Acta

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Nanostructured TiO 2 and graphene-based materials constitute components of actual interest in devices related to solar energy conversion and storage. In this work, we show that a thin layer of electrochemically reduced graphene oxide (ECrGO), covering nanostructured TiO 2 photoelectrodes, can significantly improve the photoactivity. In order to understand the working principle, ECrGO/TiO 2 photoelectrodes with different ECrGO thicknesses were prepared and studied by a set of photoelectrochemical measurements. Methanol in alkaline conditions was employed as effective hole acceptor probe to elucidate the electronic phenomena in the electrode layers and interfaces.These studies underline the hole accepting properties of ECrGO and reveal the formation of a p-n junction at the interface between ECrGO and TiO 2 . It is shown forthe first time that the resulting space charge region of about 10 nm defines the operational functionality of the ECrGO layer. Films thinner than the space charge region act as hole transport layer (HTL), which efficiently transfers holes to the liquid interface thus leading to enhanced photoactivity. Thicker films however act as hole blocking layer (HBL), resulting in a systematic decrease of the photoactivity. The finding of a thickness dependent threshold value for the operation of ECrGO as HTL and HBL is of general interest for the fabrication of optoelectronic devices with improved performance.Photoelectrochemistry is a powerful tool to elucidate the performance and working mechanism of materials and interface components used in layered optoelectronic devices, such as thin film solar cells. The resulting data reveal critical information about electronic properties such as conduction and valence band limits, as well as trapping, distribution, separation, recombination and transport of charges [1,2]. Using a simple electrochemical three-electrode configuration, photoelectrochemical measurements enable the elucidation of processes occurring at the working electrode, covering phenomena in bulk materials, across solid-solid interfaces for layered systems, as well as across the solid-liquid interface. Importantly, the acquired information provides valuable feedback for interface engineering towards optoelectronic device structures with improved performance.Materials of great current interest for solar energy conversion and storage are metal oxides such as ZnO [3] or TiO 2 [2], as well as carbon nanomaterials (graphene-based materials and carbon nanotubes) [4]. Employed as photoelectrodes [5], electron transport layers (ETLs) [6] or hole transport layers (HTLs) [7], they constitute important components in optoelectronic devices. Especially TiO 2 , graphene, and their hybrid materials are widely studied for this purpose [2,[8][9][10][11][12]. In dye-sensitized solar cells, TiO 2 is often used as the active layer, working as a photoanode [13,14]. In the case of perovskite [15] and organic solar cells [6], TiO 2 can constitute ETL [16, 17], enabling the transfer of photogenerated electrons from the ...

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Section: Photoelectrochemical Measurementssupporting

confidence: 86%

Photoactivity improvement of TiO2 electrodes by thin hole transport layers of reduced graphene oxide

Hernández‐Ferrer

Ansón‐Casaos

Víctor-Román

et al. 2019

Electrochimica Acta

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“…The high level of heat tolerance of the present OAP-containing particles is attributable to the above-mentioned particle morphology exposing ordered facets. It has been reported that rice-like titania nanorods were only stable enough to convert 2% of anatase into rutile at 1173 K [28]. Another possible reason for the heat tolerance is the presence of stabilizers, i.e.…”

Section: Resultsmentioning

confidence: 99%

Influence of Post-Treatment Operations on Structural Properties and Photocatalytic Activity of Octahedral Anatase Titania Particles Prepared by an Ultrasonication-Hydrothermal Reaction

Wei¹,

Kowalska²,

Ohtani³

2014

Molecules

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Abstract:The influence of changes in structural and physical properties on the photocatalytic activity of octahedral anatase particles (OAPs), exposing eight equivalent {101} facets, caused by calcination (2 h) in air or grinding (1 h) in an agate mortar was studied with samples prepared by ultrasonication (US; 1 h)-hydrothermal reaction (HT; 24 h, 433 K). Calcination in air at temperatures up to 1173 K induced particle shape changes, evaluated by aspect ratio (AR; d001/d101 = depth vertical to anatase {001} and {101} facets estimated by the Scherrer equation with data obtained from X-ray diffraction (XRD) patterns) and content of OAP and semi-OAP particles, without transformation into rutile. AR and OAP content, as well as specific surface area (SSA), were almost unchanged by calcination at temperatures up to 673 K and were then decreased by elevating the calcination temperature, suggesting that calcination at a higher temperature caused dull-edging and particle sintering, the latter also being supported by the analysis of particle size using XRD patterns and scanning electron microscopic (SEM) images. Time-resolved microwave conductivity (TRMC) showed that the maximum signal intensity (Imax), corresponding to a product of charge-carrier density and mobility, and signal-decay rate, presumably corresponding to reactivity of charge carriers, were increased with increase in AR, suggesting higher photocatalytic activity of OAPs than that of dull-edged particles. Grinding also decreased the AR, indicating the formation of dull-edged particles. The original non-treated samples showed activities in the oxidative decomposition of acetic OPEN ACCESSMolecules 2014, 19 19574 acid (CO2 system) and dehydrogenation of methanol (H2 system) comparable to and lower than those of a commercial anatase titania (Showa Denko Ceramics FP-6), respectively. The activities of calcined and ground samples for the CO2 system and H2 system showed almost linear relations with AR and Imax, respectively, suggesting that those activities may depend on different properties.

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“…High thermal stability of single crystalline anatase particles has recently been reported for octahedral anatase (OAPs) [48] and nanorice anatase particles [49]. It has been suggested that faceted particles, without crystal-crystal attachment points, leads to the minimization of surface energy and consequently to an increase in the activation energy of anatase to rutile transformation [25].…”

Section: Phase Contentmentioning

confidence: 99%

Decahedral-shaped anatase titania photocatalyst particles: Synthesis in a newly developed coaxial-flow gas-phase reactor

Janczarek

Kowalska

Ohtani

2016

Chemical Engineering Journal

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Decahedral-shaped anatase particles (DAPs) were prepared by a gas-phase process consisting of titanium(IV) chloride oxidation. The use of a coaxial-flow gas-phase reactor resulted in high reaction yield (ca. 70%) and good reproducibility of DAPs production. The influence of controlled and resultant preparation parameters on the process course and on DAPs properties (such as specific surface area, particle size and particle morphology) is discussed in detail.Correlations between preparation parameters and product properties indicated the best conditions for obtaining DAPs of high quality and thus with a high level of photocatalytic activity for various reaction systems.Keywords: anatase titania, decahedral-shaped particles, gas-phase synthesis, coaxial-flow reactor, photocatalytic activityconcentration of TiCl 4 vapor in gas phase (vol%) amount of powder collected from the glassfiber filter (g) length of the reaction zone (m) line speed ratio of reactant gases internal pressure (kPa) particle aspect ratio primary particle size (nm) particle shape distribution (%) particle size heterogeneity radial distance (m) reaction tube radius (m) Reynolds numbersecondary particle size (nm) specific surface area (m 2 g -1 ) amount of powder collected from the reaction tube (g) furnace temperature (K) residence time (s) average volumetric flow rate of the gas mixture (m 3 s -1 ) volumetric flow rate of argon (m 3 s -1 ) volumetric flow rate of oxygen (m 3 s -1 ) volumetric flow rate of TiCl 4 vapor (m 3 s -1 ) volumetric flow rate of TiCl 4 liquid (m 3 s -1 ) viscosity of the gas mixture (Pa s) density of the gas mixture (kg m -3 )

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Stable anatase TiO₂ formed by calcination of rice-like titania nanorod at 800 °C exhibits high photocatalytic activity

Cited by 13 publications

References 27 publications

Photoactivity improvement of TiO2 electrodes by thin hole transport layers of reduced graphene oxide

Photoactivity improvement of TiO2 electrodes by thin hole transport layers of reduced graphene oxide

Influence of Post-Treatment Operations on Structural Properties and Photocatalytic Activity of Octahedral Anatase Titania Particles Prepared by an Ultrasonication-Hydrothermal Reaction

Decahedral-shaped anatase titania photocatalyst particles: Synthesis in a newly developed coaxial-flow gas-phase reactor

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Stable anatase TiO2 formed by calcination of rice-like titania nanorod at 800 °C exhibits high photocatalytic activity

Cited by 13 publications

References 27 publications

Photoactivity improvement of TiO2 electrodes by thin hole transport layers of reduced graphene oxide

Photoactivity improvement of TiO2 electrodes by thin hole transport layers of reduced graphene oxide

Influence of Post-Treatment Operations on Structural Properties and Photocatalytic Activity of Octahedral Anatase Titania Particles Prepared by an Ultrasonication-Hydrothermal Reaction

Decahedral-shaped anatase titania photocatalyst particles: Synthesis in a newly developed coaxial-flow gas-phase reactor

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Stable anatase TiO₂ formed by calcination of rice-like titania nanorod at 800 °C exhibits high photocatalytic activity