Showing papers on "Photocatalysis published in 1983"
TL;DR: In this article, the application of photoelectrochemistry to sensitized organic photo-transformations is reviewed, and the method has the potential to modify functional groups and to assist in studying heterogeneous photocatalysis and radical ion intermediates.
Abstract: Electron-transfer mediated reactions may be initiated by long-wavelength ultraviolet or visible light irradiation of semiconductor particles. The application of this field of photoelectrochemistry to sensitized organic photo-transformations is reviewed. The method has the potential to modify functional groups and to assist in studying heterogeneous photocatalysis and radical ion intermediates.
210 citations
TL;DR: In this article, the performance of various semiconductor powders (TiO2, Fe2O3, ZnO, ZrO2 and WO3) in oxalic acid solutions were examined either in the dark or under illumination at wavelengths shorter or longer than 400 nm in the presence of oxygen.
130 citations
TL;DR: In this article, the synthesis of ammonia from N2 and H2O and its photodecomposition over SrTiO3 and BaTiOO3 based catalysts were investigated.
Abstract: Photocatalytic synthesis of ammonia from N2 and H2O and its photodecomposition were investigated over SrTiO3 and BaTiO3 based catalysts. It was demonstrated that the yield of NH3 formation increased markedly by the use of RuO2 and NiO doped three component catalysts and that photodecomposition of NH3 was coupled with photodecomposition of H2O.
64 citations
TL;DR: In this paper, a parallel-wall configuration was used for photocatalytic ammonia synthesis in a fluidized reactor of parallel wall configuration by irradiating iron-doped titanium dioxide with near ultraviolet light.
63 citations
TL;DR: In this article, the photocatalytic oxidation of liquid propan-2-ol to propanone was investigated using suspensions of TiO2 irradiated with filtered u.v. radiation at temperatures in the range 277-313 K. The activation energy for reaction on pure rutile using 366 nm radiation, 27 kJ mol−1, was independent of reaction conditions.
Abstract: The photocatalytic oxidation of liquid propan-2-ol to propanone has been investigated using suspensions of TiO2 irradiated with filtered u.v. radiation at temperatures in the range 277–313 K. The dependence of reaction rate on the square root of the intensity of the incident radiation, together with low quantum yields, reflect the dominance of photoelectron and photohole recombination within the TiO2. The activation energy for reaction on pure rutile using 366 nm radiation, 27 kJ mol–1, was independent of reaction conditions. For pure anatase, five doped rutiles and coated anatase and rutile pigments, the activation energy under standardized conditions ranged from 31 to 91 kJ mol–1. These energies are considered to reflect the solid-state properties of the catalysts rather than the chemistry of propan-2-ol oxidation, which proceeds by a radical mechanism.
63 citations
TL;DR: In this paper, the mechanism of photocatalytic hydrogen production from gaseous methanol and water was investigated, and it was shown that CO 2 and H 2 were produced by reaction between adsorbed CH 3 O(ad) and h 2 O.
36 citations
01 Jan 1983
24 citations
TL;DR: In this paper, the effects of oxygen and water on titanium dioxide photocatalyzed oxidation of benzene and toluene were examined, and it was shown that electron transfer from water and benzene to the photogenerated positive holes, synchronized with electron transferred from photoexcited titanium dioxide to oxygen, result in aromatic nuclear hydroxylation giving phenolic products and in oxidation of the side chain of toluenes affording benzyl alcohol and benzaldehyde.
Abstract: Careful examination of the effects of oxygen and water on titanium dioxide photocatalyzed oxidation of benzene and toluene has revealed that electron transfers from water and toluene to the photogenerated positive holes, synchronized with electron transfer from the photoexcited titanium dioxide to oxygen, result, respectively, in aromatic nuclear hydroxylation giving phenolic products and in oxidation of the side chain of toluene affording benzyl alcohol and benzaldehyde.
24 citations
TL;DR: In this article, negatively charged clay minerals and positively charged Al(OH)x gels were examined as catalyst supports capable of exerting such electrostatic interactions, and the tridimensional structure of the catalyst supports must be taken into account when designing a heterogeneous photocatalytic water cleavage system.
15 citations
TL;DR: In this paper, it was shown that sulfite anion (SO32−) is a sufficient hole scavenger to prevent the photocorrosion of CdS, and the effect of doped Pt on the performance of photocatalytic hydrogen evolution from water was investigated.
Abstract: Photocatalytic hydrogen evolution from water by visible light was investigated employing CdS as a semiconductor. It was demonstrated that sulfite anion (SO32−) is a sufficient hole scavenger to prevent the photocorrosion of CdS. The effect of doped Pt on CdS was also investigated, which enhanced the rate 45 times compared to the case of CdS alone.
14 citations
TL;DR: In this article, the longwavelength absorption band of ion pairs of Octacyanomolybdate was used to estimate the interionic distances between ion pairs with FeIII, CuII, UVIO2, and VIVO.
Abstract: [Mo(CN)8]4−-Ionen bilden mit FeIII, CuII, UVIO2 und VIVO farbige Ionenpaarassoziate, deren langwellige Absorptionsbanden Intervalence-Charge-Transfer-Ubergangen zugeordnet werden konnen. Durch Auswertung der Losungsmittelabhangigkeit der IT-Bande konnten die interionischen Abstande ermittelt werden.
Photocatalytic Systems. XLIV. On the Intervalence Charge Transfer Behaviour of Ion Pairs of Octacyanomolybdate
[Mo(CN)8]4− ions are forming coloured ion pairs with FeIII, CuII, UVIO2, and VIVO, the long-wavelength absorption band of which could be assigned to an intervalence charge-transfer transition. From the solvent dependence of the IT band, interionic distances could be estimated.
Patent•
02 May 1983
TL;DR: In this article, a photocatalyst layer was provided on a substrate and two kinds of compound which are oxidized or reduced by the photoexitation of the photocatalyzer and fixing a coloring compound to form a cell.
Abstract: PURPOSE:To obtain an optical conversion display element which does not require an external power source, by providing a photocatalyst layer on a substrate and using two kinds of compound which are oxidized or reduced by the photoexitation of the photocatalyst and fixing a coloring compound to form a cell. CONSTITUTION:A photocatalyst layer 12 where a semiconductor 1 such as SrTiO2 is allowed to be carried on Pt is provided on a substrate 11 such as a ''Teflon '' film of a porous structure having minutes holes. A light-transmittable substrate 13 is provided to face to the photocatalyst layer 12, and a coloring compound 3 which is excited optically by a gaseous N2 laser 2 and is oxidized or reduced and a solution 15 which a compound 4 dissolves in are charged between substrates 11 and 13, thereby obtaining an optical conversion display element. The photocatalyst layer 12 is treated with a dilute hydrochloric acid to fix methyl pyogens 3 which are colored by reduction. Ascorbic acid 4 which is achromatic even when it is oxidized is dissolved in water to obtain the solution 15. When this element is excited optically by the laser 2, coloring matters 3 are colored in blue by reduction; and thus, the optical conversion element where photocell elements are displayed in blue and an external power source is not required but only the optical energy is used is obtained.
TL;DR: In this paper, the reverse spillover was found to be the rate determining step in photoinduced lost of hydrogen by isopropanol adsorbed on TiO 2, where the hydrogen species then migrates towards Pt particles in order to be released (as dihydrogen) into the gas phase.
Abstract: Photocatalytic dehydrogenation of isopropanol at R.T. is performed on a contact associating Pt dehydrogenation catalyst with a photoactive TiO 2 carrier. Both components are required to photodehydrogenate isopropanol under u.v. irradiation. One of the steps of the reaction is the photoinduced lost of hydrogen by isopropanol (which is converted to acetone) adsorbed on TiO 2 . The hydrogen species then migrates towards Pt particles in order to be released (as dihydrogen) into the gas phase. For small density of Pt sites on TiO 2 surface (for a Pt loading smaller than 1.5%) this reverse spillover seems to be the rate determining step. This hypothesis is reinforced by the study of the influence of H 2 O in this migration.
TL;DR: In this paper, the excited charge transfer complex plays a significant role in the primary processes of photocatalysis on both unsupported and supported metal oxides and all the photocatalytic systems composed of metal oxide and reactants have been classified into four groups according to the presence or absence of both water and oxygen as reactant.
Abstract: Recent studies of the photocatalysis on metal oxides have been reviewed. The excited charge transfer complex, [Me(n-1)+—0-]* plays a significant role in the primary processes of photocatalysis on both unsupported and supported metal oxides. All the photocatalytic systems composed of metal oxides and reactants have been classified into four groups according to the presence or absence of both water and oxygen as reactant. As the initial electron or hole trapping processes associated with the formation of reaction products, the following four processes have been proposed; H++e-→H, O2+e-→O2-, OH-+h+→OH, O2-(l)+h+→O-(l). The relative importance of the four processes varies with the group of photocatalytic systems. The significance of the studies of excited states of metal oxides as well as the reaction intermediates has been emphasized. Finally, the correlation of photocatalysis on metal oxides for utilization of solar energy has been mentioned.
TL;DR: In this article, the mechanism of photoelectrocatalytic dehydrogenation of 2-propanol on a ZnO photo-electrode is re-examined.
TL;DR: In this article, it was shown that UV photolysis of AgI is accompanied by the fixation of N2, whether it occurs in an atmosphere of that gas or in air.
Abstract: The photodecomposition of AgI is but one of the many transformations which natural, anthropogenic and artificial aerosols undergo under light. Our aim here is to show that UV photolysis of AgI is accompanied by the fixation of N2, whether it occurs in an atmosphere of that gas or in air.
01 Jan 1983
TL;DR: Etudes des reactions photoelectrochimiques et photocatalytiques du propionate de sodium en presence de ZnO polycristallin, un semi-conducteur, oxyde, du type n (intervalle des bandes: 3,2 eV; absorption maximum a 365 nm).
Patent•
10 Sep 1983
TL;DR: In this paper, a semiconductor photocatalyst is dispersed in toluene and the dispersion is irradiated with light of 200-1,000nm/hr in an inert gas such as nitrogen gas, preferably at room temperature to produce bibenzyl.
Abstract: PURPOSE:Using a semiconductor with a specific band gap as a catalyst, inexpensive toluene is irradiated with light to produce bibenzyl easily in high selectivity, which is used as an intermediate of styrene or of a variety of derivatives. CONSTITUTION:A semiconductor photocatalyst is dispersed in toluene and the dispersion is irradiated with light of 200-1,000nm/hr in an inert gas such as nitrogen gas, preferably at room temperature to produce bibenzyl. The semiconductor has a band gap of less than 5.0eV and, e.g., titanium oxide, tungsten oxide or their combination is used. Further, in order to increase the oxidation- reduction performance, a Pt, Pd or Au compound such as sodium chloroplatinate is added as a semiconductor electrode to effect photovoltaic reaction. The amount of the catalyst is 0.01-10pts. per 100pts. of the toluene on the reaction preferably.
TL;DR: In this article, it was discovered that sulfur is directly oxidized to SO/sub 4/sup 2 -/, i.e., sulfuric acid, on a TiO/sub 2/ photocatlyst in a suspension into which O/sub 1/s bubbled, and the reaction mechanism of this photocatalytic oxidation of sulfur is discussed on the basis of various experimental data.
Abstract: It was discovered that sulfur is directly oxidized to SO/sub 4//sup 2 -/, i.e., sulfuric acid, on a TiO/sub 2/ photocatlyst in a suspension into which O/sub 2/ bubbled. The photocatalytic oxidation is assigned to the electron and hole produced by light of shorter wavelength than about 400 nm, although sulfur itself photoreacts in light of less than about 300 nm. The oxidation reaction is photocatalyzed on anatase but not on rutile, and its rate is faster in alkaline solution than in water and acid. It was found that H/sub 2/S is simultaneously produced as well as SO/sub 4//sup 2 -/ in water. The reaction mechanism of this photocatalytic oxidation of sulfur is discussed on the basis of the various experimental data. The direct production of sulfuric acid was confirmed by a sunlight illumination test.