2009 Photoeletrochemical generation of hydrogen over carbon-doped TiO2 photoanode (Zhou et al).pdf (original) (raw)
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Photoeletrochemical generation of hydrogen over carbon-doped TiO2 photoanode
Applied Catalysis B-environmental, 2009
Nanostructured carbon-doped TiO 2 (C-TiO 2) thin film was prepared by pulsed laser deposition (PLD) on ITO substrate. Results of X-ray diffraction (XRD) analysis of the thin film showed that the crystal structure of the C-TiO 2 was a hybrid of rutile and anatase. Data of X-ray photoelectron spectroscopic (XPS) analysis confirmed the successful incorporation of carbon into TiO 2 molecules, which formed defects. These defects narrowed the band gap of the C-TiO 2 from 3.25 eV of pure TiO 2 to 3.15 eV. The photoelectrochemical property of the C-TiO 2 film was examined by evaluating the efficiency of hydrogen generation by water splitting in a two-compartment electrochemical system. The fastest rate of gas production was obtained when the thin film was irradiated by light at a wavelength of 325 nm; the photoresponse under visible radiation was limited, however. Applying a bias potential across the photoanode and its counter electrode can increase hydrogen generation effectively. Organic substance added to the photoanodic chamber was photocatalytically degraded which increased the photocurrent and subsequently enhanced hydrogen generation.
Study of N-doped TiO2 thin films for photoelectrochemical hydrogen generation from water
Open Chemistry, 2015
The present work deals with nitrogen-doped stoichiometric TiO2:N and non-stoichiometric TiO2−x:N thin films deposited by means of dc-pulsed reactive sputtering for application as photoanodes for hydrogen generation from water, using solar energy. Stoichiometric thin films of TiO2 crystallize as a mixture of anatase and rutile while rutile phase predominates in TiO2:N at higher nitrogen flow rates as shown by X-ray diffraction at grazing incidence, XRD GID. Lack of bulk nitridation of stoichiometric TiO2:N is indicated by valence-to-core X-ray emission spectroscopy, XES, analysis. The energy band gap as well as flat band potential remain almost unaffected by increasing nitrogen flow rate in this case. In contrast to that, non-stoichiometric thin films of TiO2‑x:N demonstrate systematic evolution of the structural, morphological, optical and photolectrochemical properties upon increasing level of nitrogen doping. Pronounced changes in the growth pattern of non-stoichiometric TiO2-x:N ...
International Journal of Hydrogen Energy, 2008
Carbon modified n-type titanium oxide ðCM-n-TiO 2 Þ photoelectrodes were synthesized by flame oxidation of 0.2 mm thick Ti metal sheets for hydrogen production by photoelectrochemical splitting of water. The photocurrent density at optimized CM-n-TiO 2 photoelectrodes (synthesized using flame temperature of 825 C and oxidation time of 15 min) was found to be 6:38 mA cm À2 at a minimal external applied potential of 0.24 V under illumination with light intensity of 70 mW cm À2 from a 150 Watt Xenon Lamp. The same value of photocurrent density was found when the wavelength dependent photocurrent densities at the same applied potential of 0.24 V were integrated. This optimized CM-n-TiO 2 photoelectrode was found to split water with maximum photoconversion efficiency of 9.02% under white light illumination. Also, a very close value of photoconversion efficiency of 9.01% was obtained from the wavelength dependent photocurrent density, j p ðlÞ under monochromatic light illumination. Carbon modification lowered the original bandgap energy from 3.0 to 2.65 eV and generated a mid-gap band at 1.6 eV above the valence band of the optimized CM-n-TiO 2. Photocurrent measurements, UV-Vis spectra, X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) were used to characterize CM-n-TiO 2 photoelectrodes.
TiO2based systems for photoelectrochemical generation of solar hydrogen
Journal of Physics: …, 2009
In the present work our attention was focused on the obtaining photoelectrodes for photoelectrochemical cell (PEC) that incorporate two electrodes, one of which has been titania (TiO 2 ) coated on a transparent conducting oxide (TCO), referred to as the primary electrode and the other, the counter electrode, a non-corrosive metal such as a thin layer of platinum. A thin layer of a nanoporous TiO 2 semiconductor was deposited onto a sheet of ITO conducting glass (sheet resistance ~ 30 cm -2 ). Several complementary investigation techniques like BET, SEM and XRD were used to follow the influence of the reactants molar ratio and thermal treatment on the TiO 2 photoanode. The nanocrystalline TiO 2 /ITO conducting glass electrode seems to be a promising photoanode in a photoelectrochemical PEC cell for hydrogen generation by water splitting.
International Journal of Hydrogen Energy, 2012
Hydrogen energy Photoelectrochemical process a b s t r a c t Carbon-incorporated titanium dioxide (TiO 2 ) photoelectrodes with different structural features were prepared via rapid-anodic oxidation under different electrical potentials and exposure times. The interstitial carbon arising from the pyrogenation of ethylene glycol electrolytes induced a new C2p occupied state at the bottom of the conduction band, which lowered the band gap energy to w2.3 eV and consequently enabled the visible-light responsiveness. Photoelectrodes with nanotubular structures provided higher photoconversion efficiency (h) and hydrogen (H 2 ) evolution capability than those with irregular structures. The increased aspect ratio, wall thickness, and pore size of the nanotube arrays contributed to h through greater photon excitation and penetration. However, this contribution is limited by the high recombination of the charge carriers at ultra-high aspect ratios. Photoelectrodes with a nanotube length of w19.5 mm, pore size of w103 nm, wall thickness of w17 nm, and aspect ratio of w142.5 exhibited remarkable capability to generate H 2 at an evolution rate of up to w508.3 mL min À1 cm À2 and h of w2.3%.
International Journal of …, 2008
TiO 2 RF magnetron sputtering Sol-gel method Visible light irradiation a b s t r a c t TiO 2 thin films have been synthesized by radio-frequency magnetron sputtering and solgel method to study the hydrogen generation by photocatalytic water splitting under visible light irradiation. Photoelectrochemical cell with chemical bias, involving photoanode in form of TiO 2 film deposited on conducting indium tin oxide (ITO) film and Pt as cathode, is developed. The effect of conducting ITO layer on photo-voltage is studied by varying the thickness of ITO films. Constant H 2 generation rate is obtained for long period of time by both the TiO 2 films because of the separated evolution of H 2 and O 2 gas, thus eliminating the back-reaction effect. Sputter-deposited film as compared to sol-gelsynthesized film showed better H 2 generation rate, mainly explained in terms of the higher visible light absorption achieved by oxygen vacancies created in the TiO 2 film by the energetic target ions during deposition in pure Ar gas pressure. ª (R. Dholam). A v a i l a b l e a t w w w . s c i e n c e d i r e c t . c o m j o u r n a l h o m e p a g e : w w w . e l s e v i e r . c o m / l o c a t e / h e
This paper reports the investigations on the optimization of nanostructured TiO2 with respect to optimum photoelectrode area for modular design of photoelectrolysis cell. This was done for determining the electrode area for optimum electrical output and hydrogen production rate. The nanostructured TiO2 has been formed by hydrolysis of titanium tetraisopropoxide Ti[OCH(CH3)2]4 followed by the deposition with spin on technique. The photoelectrochemical cell having nanostructured TiO2 photoanode of several geometricareas, namely, 0.21, 0.50, 0.72, 1.47 and 1:85 cm2, were fabricated and characterized. It has been found that the photoanode area corresponding to optimum electrical output and hydrogen production rate corresponds to ∼ 0:5 c m2.
In the present work our attention was focused on the obtaining photoelectrodes for photoelectrochemical cell that incorporate two electrodes, one of which has been titania (TiO 2 ) coated on a transparent conducting oxide (TCO), referred to as the primary electrode and the other, the counter electrode, a non-corrosive metal such as a thin layer of platinum. A thin layer of a nanoporous TiO 2 semiconductor was deposited onto a sheet of ITO conducting glass (sheet resistance ~ 30 Ωcm -2 ). Several complementary investigation techniques like BET, SEM and XRD were used to follow the influence of the reactants molar ratio and thermal treatment on the TiO 2 photoanode. The nanocrystalline TiO 2 /ITO conducting glass electrode seems to be a promising photoanode in a photoelectrochemical cell for hydrogen generation by water splitting.
A study of S-doped TiO2 for photoelectrochemical hydrogen generation from water
Journal of Materials Science, 2008
Sulfur-doped titanium dioxide (TiO 2 ) was investigated as a potential catalyst for photoelectrochemical hydrogen generation. Three preparation techniques were used: first ballmilling sulfur powder with Degussa P25 powder (P25), second, ball milling thiourea with P25, and third a sol-gel technique involving titanium (IV) butoxide and thiourea. The resulting powders were heat-treated and thin-film electrodes were prepared. In all three cases, the heat-treated powders contained small amounts of S (1-3%). However, Rietveld analysis on X-ray diffraction (XRD) measurements revealed no significant changes in lattice parameters. For the samples prepared using thiourea, X-ray photoelectron spectroscopy (XPS) measurements indicated the presence of N and C in the heat-treated powders in addition to S. In all cases, visible-ultraviolet spectroscopy performed on bulk powders confirmed the extension of absorption into the visible region. However, the same spectroscopic technique performed on thin-film electrodes (*0.5 lm) suggests that the absorption coefficients were very small in the visible region (B10 4 m -1 ). The first and third methods yielded powders with substantially smaller photocatalytic activity relative to P25 powder in the UV region. The electrodes prepared from powders obtained using the second method yielded photocurrents comparable to those prepared from P25 powder.
International Journal of Hydrogen Energy, 2010
Photocatalytic TiO 2 thin films were prepared via an electron beam-induced deposition (EBID) method. The effects of post-calcination treatment on the properties of the prepared TiO 2 thin films were studied. X-ray diffraction (XRD), scanning electron microscope-energy dispersive spectrometry (SEM-EDS), and UVeV is absorption spectrometry were performed to reveal the crystallinity, surface morphology, chemical composition, and light absorbance of the prepared TiO 2 thin films. The photoelectrochemical characteristics of the TiO 2 thin films were investigated with a potentiostat. Under UV irradiation, a photocurrent of e2.1 mA was observed for the TiO 2 thin film with post-calcination at 500 C. A water-splitting reaction was conducted over the TiO 2 thin film with the best photoelectrochemical performance. The yields of hydrogen and oxygen were 59.8 and 30.6 mmole, respectively, after 8 h of reaction under UV irradiation.