-
[show abstract]
[hide abstract]
ABSTRACT: Brought to light: Thin, planar nanojunctions between layered MoS(2) and graphitic CN (g-CN) were constructed and allowed fast charge separation across the junction interfaces to facilitate hydrogen photosynthesis. This research represents a proof of concept for the rational fabrication of thin interfacial junctions between co-catalysts and semiconductors having similar layered geometric structures.
Angewandte Chemie International Edition 02/2013; · 13.45 Impact Factor
-
Yidong Hou,
Billie L Abrams,
Peter C K Vesborg,
Mårten E Björketun,
Konrad Herbst,
Lone Bech,
Alessandro M Setti,
Christian D Damsgaard,
Thomas Pedersen,
Ole Hansen,
Jan Rossmeisl,
Søren Dahl,
Jens K Nørskov,
Ib Chorkendorff
[show abstract]
[hide abstract]
ABSTRACT: The production of fuels from sunlight represents one of the main challenges in the development of a sustainable energy system. Hydrogen is the simplest fuel to produce and although platinum and other noble metals are efficient catalysts for photoelectrochemical hydrogen evolution, earth-abundant alternatives are needed for large-scale use. We show that bioinspired molecular clusters based on molybdenum and sulphur evolve hydrogen at rates comparable to that of platinum. The incomplete cubane-like clusters (Mo(3)S(4)) efficiently catalyse the evolution of hydrogen when coupled to a p-type Si semiconductor that harvests red photons in the solar spectrum. The current densities at the reversible potential match the requirement of a photoelectrochemical hydrogen production system with a solar-to-hydrogen efficiency in excess of 10%. The experimental observations are supported by density functional theory calculations of the Mo(3)S(4) clusters adsorbed on the hydrogen-terminated Si(100) surface, providing insights into the nature of the active site.
Nature Material 06/2011; 10(6):434-8. · 32.84 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: We report here on a study of vertically aligned TiO(2) nanotube arrays grown by the one-step anodic oxidation technique and their photocatalytic performance for methane decomposition. Quantitative activity data as a function of film thickness is obtained.
Chemical Communications 03/2011; 47(9):2613-5. · 6.17 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Gas-phase photooxidation of CO over TiO2 catalysts (P25 and TiO2 nanotubes) in μ-reactors with quantitative product detection was used to study turnover as a function of illumination intensity over 4 orders of magnitude. Turnover was found to be of order 0.84 in illumination intensity. A CO photooxidation action spectrum was also recorded for TiO2 nanotubes. The action spectrum was used to calculate both the incident photon to product efficiency (IPPE) and the absorbed photon to product efficiency (APPE). The wavelength dependence of the IPPE was found to follow the absorption spectrum while the APPE was found to have a peak around 345 nm with a value of about 0.8%.
06/2010;
-
[show abstract]
[hide abstract]
ABSTRACT: Porous nanocrystalline ZnGa2O4 catalysts were synthesized by a simple soft-chemical method at low temperature. The catalysts were characterized by XRD, nitrogen adsorption, SEM, TEM, UV/ vis, and FT-IR spectroscopy. The activity of the photocatalysts was evaluated by decomposition of benzene and its derivatives in the gas phase. It was found that hydrothermal treatment resulted in the formation of spinel ZnGa2O4 with a large surface area of 43-201 m2 x g(-1) depending on the synthetic temperature. The optimum synthetic temperature was found to be 80 degrees C, at which the sample possessed a surface area of 201 m2 x g(-1) and had the highest photocatalytic activity for degrading benzene. A comparison with TiO2 and Pt/TiO2 showed that the ZnGa2O4 (synthesized at 80 degrees C) had improved photocatalytic activity and durability over the TiO2-based catalysts. No remarkable deactivation of the ZnGa2O4 catalyst was observed in 80 h photoreaction, whereas the TiO2 deactivated remarkably in 24 h reaction. The high photocatalytic performance of porous ZnGa2O4 catalysts can be explained by the large specific surface area, the accessible porous framework, and the high redox power.
Environmental Science and Technology 09/2009; 43(15):5947-51. · 5.23 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: We investigated semiconductor characteristics for polymeric carbon nitride as a metal-free photocatalyst working with visible light and have shown that the efficiency of hydrogen production by photochemical water reduction can be improved by approximately 1 order of magnitude by introducing the right type of mesoporosity into polymeric C(3)N(4). We anticipate a wide rang of potential application of C(3)N(4) as energy transducers for artificial photosynthesis in general, especially with a 3D continuous nanoarchitecture. Moreover, the results of finding photoactivity for carbon nitride nanoparticles can enrich the discussion on prebiotic chemistry of the Earth, as HCN polymer clusters are unequivocal in the solar system.
Journal of the American Chemical Society 03/2009; 131(5):1680-1. · 9.91 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Zn(2)GeO(4) nanorods were prepared by a surfactant-assisted hydrothermal method and used as photocatalysts for the decomposition of organic pollutants in water. The physicochemical properties of the Zn(2)GeO(4) photocatalysts were characterized by several techniques, and their photocatalytic activity was evaluated by the decomposition of methyl orange, salicylic acid, and 4-chlorophenol in aqueous solution. The results revealed that the Zn(2)GeO(4) nanorods have a much higher photocatalytic activity for decomposing organic pollutants in aqueous solution than both Zn(2)GeO(4) prepared by a conventional solid-state reaction and widely used TiO(2) (Degussa P25). There is no obvious deactivation of Zn(2)GeO(4) nanorods in the photocatalytic reactions. The intermediates of the photocatalytic reactions were monitored by LC-MS, and possible photocatalytic reaction pathways as to how Zn(2)GeO(4) nanorods degrade organic dyes were proposed.
ChemSusChem 01/2009; 1(12):1011-9. · 6.83 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: A rod-shaped Zn2GeO4 photocatalyst has been successfully prepared by a surfactant-assisted hydrothermal method. The photocatalyst was characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, thermogravimetric analysis, UV/vis, N2 adsorption-desorption, and FTIR techniques. The photocatalytic activity of the sample was evaluated by the decomposition of benzene in the gas phase under UV light illumination and was compared with that of bulk Zn2GeO4, commercial titania (Degussa P25), and Pt/P25. The results revealed that the Zn2GeO4 nanorods had the best photocatalytic activity for mineralizing benzene to CO2 among the catalysts examined. No obvious deactivation of Zn2GeO4 nanorods was observed during the prolonged operation of 140 h. It was found that the Zn2GeO4 was also more active and stable than TiO2-based catalysts toward photocatalytic decomposition of other volatile aromatic pollutants (e.g., toluene and ethylbenzene).
Environmental Science and Technology 11/2008; 42(19):7387-91. · 5.23 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: A porous beta-Ga2O3 photocatalyst has been successfully prepared. The photocatalyst was characterized by XRD, N2 adsorption-desorption, TEM, UV/vis, and FTIR techniques. The photocatalytic activity of the sample was evaluated by the decomposition of benzene in air under UV light illumination and was compared with that of the commercial titania (Degussa P25) and Pt/P25. Results revealed that the synthesized Ga2O3 was porous beta-Ga2O3 and was highly photoactive for mineralizing benzene and its derivatives (e.g., toluene and ethylbenzene) to CO2 under ambient conditions. The photocatalytic conversion of benzene over beta-Ga2O3 was about 1 order of magnitude higher than that over P25, and no obvious deactivation of beta-Ga2O3 was observed during the prolonged operation of 80 h. The high activity and long-term stability of the Ga2O3 have been ascribed to its stronger oxidative capability and higher specific surface area in comparison with P25.
Environmental Science and Technology 10/2006; 40(18):5799-803. · 5.23 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Light-harvesting macroporous channels have been successfully incorporated into a mesoporous TiO(2) framework to increase its photocatalytic activity. This bimodal porous material was characterized by X-ray diffractometry in both low-angle and wide-angle ranges, N(2) adsorption-desorption analysis, scanning and transmission electron microscopy, FT-IR, and diffuse reflectance spectroscopy. Ethylene photodegradation in gas-phase medium was employed as a probe reaction to evaluate the photocatalytic reactivity of the catalysts. The results reveal that sintering temperature significantly affects the structural stability and photocatalytic activity of titania. The catalyst which calcined at 350 degrees C possessed an intact macro/mesoporous structure and showed photocatalytic reactivity about 60% higher than that of commercial P25 titania. When the sample was calcined at 500 degrees C, the macroporous structure was retained but the mesoporous structure was partly destroyed. Further heating at temperatures above 600 degrees C destroyed both macro- and mesoporous structures, accompanied by a loss in photocatalytic activity. The high photocatalytic performance of the intact macro/mesoporous TiO(2) may be explained by the existence of macrochannels that increase photoabsorption efficiency and allow efficient diffusion of gaseous molecules.
Langmuir 04/2005; 21(6):2552-9. · 4.19 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Functionalized mesoporous TiO2 molecular sieves were prepared by treating ordered mesoporous TiO2 with phosphoric acid or ammonium sulfate at high temperature. The samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), N2 adsorption–desorption measurement, X-ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectrometer (FT-IR). The photocatalytic activity of the samples was evaluated by photocatalytic decomposition of bromomethane (CH3Br) in air. Results revealed that the functionalized TiO2 samples preserved ordered mesostructure and exhibited enhanced physicochemical properties. The photocatalytic activity of the functionalized mesoporous TiO2 sample was about three times higher than that of the pure mesoporous TiO2. The concentrations of phosphoric acid and ammonium sulfate solutions used for the functionalization of TiO2 greatly influenced the photocatalytic activity of the resultants materials. The optimal concentrations of phosphoric acid and ammonium sulfate solutions were 0.05 and 0.10 M, respectively. The enhanced photocatalytic performance of the functionalized mesoporous TiO2 could be attributed to large specific surface area, high hydroxyl density, and enhanced surface chemical state.
Microporous and Mesoporous Materials 110:543-552. · 3.29 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Nitrogen-doping (N-doping) is a popular strategy for promoting the absorption of visible light in TiO2 and other photocatalysts. We have grown TiO2 nanotubes onto non-conducting Pyrex in a one step process via single layer titanium films. In an attempt to improve the self-cleaning ability of vertically aligned TiO2 nanotube arrays under visible light irradiation we have doped them with nitrogen and tested the resulting nanotube films by two representative test methods. The first method is an established dye-test which is typically used as a “quick-and-dirty” screening for activity. The second method is the gas-phase oxidation reaction of CO-oxidation and methane. The encouraging results of the dye tests are in conflict with the discouraging results of the gas-phase tests. The fact that the dye test gives a “false positive” underscores the dangers of extrapolating photocatalytic performance results from dye decoloration tests to more difficult redox reactions such as hydrocarbon mineralization.Highlights► Vertically aligned nitrogen doped TiO2 nanotubes were coated onto non-conducting Pyrex. ► Comparison of photocatalytic reduction of Rz dye and photocatalytic oxidation of CO and CH4. ► The results of the dye tests are in conflict with the results of the gas-phase tests. ► This result demonstrates the need to confirm photocatalytic activity using various test methods.
Journal of Photochemistry and Photobiology A: Chemistry. 222(1):258-262.
-
[show abstract]
[hide abstract]
ABSTRACT: Postnitridation annealing has a remarkable effect on the surface property and photocatalytic performance of N-doped TiO2 for photocatalytic oxidation of ethylene. The activity of N-doped TiO2 under visible light illumination (λ>420 nm) can be enhanced fourfold by annealing the sample at 400 °C. Characterization results show that the thermal annealing reduces surface oxygen vacancies, removes surface-adsorbed NH3, and facilitates the adsorption of molecular oxygen on catalyst surface. Such a surface reconstruction contributes to the enhanced photocatalytic activity of the N-doped TiO2. The postcalcination also improves the photocatalytic stability of the N-doped TiO2 by stabilizing nitrogen atoms in the TiO2 lattice. A N-doped TiO2 sample without postcalcination suffers from a gradual deactivation, due mainly to the passivation of the catalyst surface by oxidized nitrogen species (e.g., hyponitrite, nitrite ions, and nitrate ions) formed during the photocatalytic degradation of ethylene.
Journal of Catalysis. 255(1):59-67.
