Combinatorial atmospheric pressure chemical vapour deposition (cAPCVD) of niobium doped anatase; effect of niobium on the conductivity and photocatalytic activity

Kafizas, Andreas; Dunnill, Charles W.; Parkin, Ivan P.

doi:10.1039/c0jm01244k

Cited by 53 publications

(70 citation statements)

References 57 publications

(105 reference statements)

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“…The synthetic process involved the reaction of a titanium source (titanium tetrachloride, TiCl 4 ) with an oxygen source (ethyl acetate, EtAc) and a respective dopant source at 500 or 550 C. Niobium pentachloride (NbCl 5 ) was used as a Nb source, tungsten Table 1 The synthetic conditions use to produce the combinatorial film that contained the minimum electrical resistivity across each series (Nb, W, N and F:TiO 2 ) by combinatorial atmospheric pressure chemical vapour deposition (APCVD) a hexachloride (WCl 6 ) was used as a W source, ammonia (NH 3 ) was used as a N source and triuoroacetic acid (F 3 C 2 O 2 H) was used as a F source. Within the Nb:TiO 2 and W:TiO 2 systems a characteristic blue tinge 14,18 was observed that increased in intensity at higher doping levels. The lms showed colour bands when viewed off-angle due to variations in lm-thickness, a characteristic of TiO 2based thin-lms.…”

Section: Physical Characteristics Of Each Combinatorial Systemmentioning

confidence: 99%

“…31 It would therefore be of great benet to use this industrially established synthetic route to attempt to improve the properties of TiO 2 in order to maintain future applicability. 14,18,[33][34][35][36][37] Traditionally, precursors are homogenised before reaction, whereas in cAPCVD precursors are introduced separately during the reaction. 32 Interestingly, TiO 2 thin-lms with signicant variations in phase, thickness and doping level can be achieved using a combinatorial approach (cAPCVD).…”

Section: Introductionmentioning

confidence: 99%

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TiO2-based transparent conducting oxides; the search for optimum electrical conductivity using a combinatorial approach

et al. 2013

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A series of Nb, W, N and F:TiO 2 thin-film systems were grown by a combinatorial atmospheric pressure chemical vapour deposition (APCVD) process. Conditions were varied in each experiment to produce a series of films with compositional gradient. For each system, the electrical resistivity at a number of positions (up to 200 on each film) was screened using a high-throughput tool. This allowed easy identification of the material with the lowest electrical resistivity across a reservoir of combinatorially produced samples. The most conductive material within each system was analysed in depth by X-ray photoelectron spectroscopy, wavelength dispersive X-ray analysis, X-ray diffraction, Raman spectroscopy, scanning electron microscopy, UV-visible-NIR spectroscopy and Hall effect measurements. The most electrically conductive materials are found in the F:TiO 2 [F s z 4-5%, r ¼ 0.21 U cm, m ¼ 3.6 cm 2 V À1 s À1 , n ¼ 8.1 Â 10 18 cm À3 ] and Nb:10 18 cm À3 ] systems. The electrical resistivities reported for Nb:TiO 2 and W:TiO 2 are the best to date for materials grown by APCVD. Extensive comparisons with the literature are made and summarised in this report.

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Section: Physical Characteristics Of Each Combinatorial Systemmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

TiO2-based transparent conducting oxides; the search for optimum electrical conductivity using a combinatorial approach

et al. 2013

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“…166,181 The material has been studied using a novel combinatorial AACVD (cAACVD) methodology (Fig. 190 Combinatorial AACVD was used for the first time to produce films of gallium-indium-oxide which showed compositional gradient across the surface. The set up for cAACVD has two separate inlets, which when one is loaded with dopant and the other the main precursor gives rise to the production of films with a compositional gradient.…”

Section: Ternary Main Group Tcosmentioning

confidence: 99%

Solution based CVD of main group materials

2016

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This critical review focuses on the solution based chemical vapour deposition (CVD) of main group materials with particular emphasis on their current and potential applications. Deposition of thin films of main group materials, such as metal oxides, sulfides and arsenides, have been researched owing to the array of applications which utilise them including solar cells, transparent conducting oxides (TCOs) and window coatings. Solution based CVD processes, such as aerosol-assisted (AA)CVD have been developed due to their scalability and to overcome the requirement of suitably volatile precursors as the technique relies on the solubility rather than volatility of precursors which vastly extends the range of potentially applicable compounds. An introduction into the applications and precursor requirements of main group materials will be presented first followed by a detailed discussion of their deposition reviewed according to this application. The challenges and prospects for further enabling research in terms of emerging main group materials will be discussed.

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“…4 In an effort to decrease the bandgap of TiO2, and increase solar activity, TiO2 has been doped with nitrogen, 5,6 sulphur, 7 fluorine 8 and other elements. 9,10 However, coupling TiO2 with narrow bandgap semiconductors and forming heterojunctions can result in synergistic improvements in activity, and may be the more promising strategy. 11,12 Since the first definitive proof that photocatalytic water oxidation in plants occurs on a manganese cluster (photo-system II), 13 numerous mimics have emerged.…”

Section: Introductionmentioning

confidence: 99%

Water Oxidation Kinetics of Accumulated Holes on the Surface of a TiO₂ Photoanode: A Rate Law Analysis

et al. 2017

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ABSTRACT. It has been more than 40 years since Fujishima and Honda demonstrated water splitting using TiO2, yet there is still no clear mechanism by which surface holes on TiO2 oxidize water. In this article, we use a range of complementary techniques to study this reaction that provide a unique insight into the reaction mechanism. Using transient photocurrent (TPC) and 2 transient absorption spectroscopy (TAS), we measure both the kinetics of electron extraction (t50% ~200 µs, 1.5 VRHE) and the kinetics of hole oxidation of water (t50% ~100 ms, 1.5 VRHE) as a function of applied potential, demonstrating the water oxidation by TiO2 holes is the kinetic bottleneck in this water splitting system. Photo-induced absorption spectroscopy (PIAS) measurements under 5 s LED irradiation are used to monitor the accumulation of surface TiO2 holes under conditions of photo-electrochemical water oxidation. Under these conditions we find that the surface density of these holes increases non-linearly with photocurrent density. In alkali (pH 13.6), this corresponded to a rate law for water oxidation that is 3 rd order with respect to surface hole density, with a rate constant = 22 ± 2 nm 4 .s -1 . Under neutral (pH = 6.7) and acidic (pH = 0.6) conditions the rate law was 2 nd order with respect to surface hole density, indicative of a change in reaction mechanism. Although a change in reaction order was observed, the rate of reaction did not change significantly over the wide pH range examined (with TOFs per surface hole in the region of 20 -25 s -1 at ~1 sun irradiance). This showed that the rate limiting step does not involve OH -nucleophilic attack and demonstrated the versatility of TiO2 as an active water oxidation photocatalyst over a wide range of pH.TOC graphic

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Combinatorial atmospheric pressure chemical vapour deposition (cAPCVD) of niobium doped anatase; effect of niobium on the conductivity and photocatalytic activity

Cited by 53 publications

References 57 publications

TiO2-based transparent conducting oxides; the search for optimum electrical conductivity using a combinatorial approach

TiO2-based transparent conducting oxides; the search for optimum electrical conductivity using a combinatorial approach

Solution based CVD of main group materials

Water Oxidation Kinetics of Accumulated Holes on the Surface of a TiO₂ Photoanode: A Rate Law Analysis

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Combinatorial atmospheric pressure chemical vapour deposition (cAPCVD) of niobium doped anatase; effect of niobium on the conductivity and photocatalytic activity

Cited by 53 publications

References 57 publications

TiO2-based transparent conducting oxides; the search for optimum electrical conductivity using a combinatorial approach

TiO2-based transparent conducting oxides; the search for optimum electrical conductivity using a combinatorial approach

Solution based CVD of main group materials

Water Oxidation Kinetics of Accumulated Holes on the Surface of a TiO2 Photoanode: A Rate Law Analysis

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Product

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Water Oxidation Kinetics of Accumulated Holes on the Surface of a TiO₂ Photoanode: A Rate Law Analysis