Showing papers on "Photocatalysis published in 1986"
TL;DR: The spectral sensitization of TiO2 in this case was concluded to be due to NOx impurity which was formed from NF4OH used in the preparation of titanium hydroxide as mentioned in this paper.
669 citations
TL;DR: In this paper, the mechanism of photocatalytic decomposition of H2O into H2 and O2 over NiO and SrTiO3 powder was studied on the basis of the structure of the catalyst.
369 citations
TL;DR: The structure of NiO-SrTiO/sub 3/ powder has been studied by spectroscopic methods such as SEM, TEM, EXAFS, XANES, and XPS as mentioned in this paper.
Abstract: The structure of NiO-SrTiO/sub 3/ powder, which is a photocatalyst for the decomposition of water into H/sub 2/ and O/sub 2/, has been studied by spectroscopic methods such as SEM, TEM, EXAFS, XANES, and XPS. It has been clearly shown that the active catalyst has a peculiar structure; that is, nickel metal exists at the interface of NiO and SrTiO/sub 3/. The surface of NiO changes further into Ni(OH)/sub 2/ during the photocatalytic reaction in water. 31 references, 7 figures, 2 tables.
343 citations
TL;DR: In this article, the photocatalytic activity of TiO/sub 2/ species in the titanium-silicon oxides was found to be enhanced in the region of lower Ti content.
Abstract: Photocatalytic reactions of alkenes and alkynes with water were investigated over titanium-silicon oxides in order to obtain information about the potential ability of binary oxides as photocatalysts. Photocatalytic activity of TiO/sub 2/ species in the titanium-silicon oxides was found to be enhanced in the region of lower Ti content. X-ray, photoluminescence, and X-ray photoelectron spectroscopy (XPS) measurements indicate that Ti ions are enriched on the surface of the oxides having a low Ti content and present separately from each other in the SiO/sub 2/ matrix. From these results, together with those obtained with highly dispersed TiO/sub 2/ anchored on support surfaces, it is suggested that the higher photocatalytic activity of such catalysts is due to the diminished radiationless transfer of the photon energy absorbed by TiO/sub 2/. 18 references, 7 figures, 3 tables.
209 citations
01 Jan 1986
TL;DR: Hiskia et al. as mentioned in this paper studied the role of catalysts in photoelectrochemical phenomena, focusing on the performance of colloidal and heterogeneous redox catalysts.
Abstract: Photoinduced charge separation: Requirements needed for ideal relays and photosensitizers- Photoinduced charge separation: Towards the design of supermolecular systems based on transition metal complexes- Fundamental studies into primary events in photocatalysis employing CdS and TiO semiconductors: Photoluminescence, laser flash photolysis and pulse radiolysis- Dynamics of interfacial electron transfer reactions in colloidal semiconductor systems and water cleavage by visible light- Electronic Spectroscopy of semiconductor clusters- Catalysed decay of oxidising radicals in water- Photocatalysis and light-induced electron transfer reactions of tertiary amines- Photocatalytic production of ascorbic acid A secondary photosynthesis in plants- Spectroscopic and electrochemical studies of photochemical electron transfer in linked donor-acceptor molecules- Bifunctional porphyrins: Redox photochemistry of: meso(tritolyl(pyridyl Ru(III) (NH 3) 4 L')) porphyrin: (L'=NH 3, pyridine, 5-Cl-pyridine)- Linear chain platinum complexes as photocatalysts- Electron transfer reactions on extremely small semiconductor colloids studied by pulse radiolysis- Nafion stabilized aqueous solutions of colloidal semiconductors- In situ generated catalyst-coated colloidal semiconductor CdS particles in surfactant vesicles and polymerized surfactant vesicles- Development of catalysts for water photoreduction: Improvement, poisoning and catalytic mechanism- Radiolytic methods of preparation of colloidal and heterogeneous redox catalysts and their application in light-induced H2 generation from water- The effect of promoters on the photochemical water cleavage in suspensions of Pt-loaded TiO2 with increased light to chemical conversion efficiency- Metallic catalysts on semiconductors: Transparency and electrical contact properties- On the nature of the inhibition of electron transfer at illuminated p-type semiconductor electrodes- The importance of solution kinetics in photoelectrochemical phenomena- Mechanistic aspects of semiconductor photoelectrochemistry: The behavior of Si and GAAs in nonaqueous solvents- Charge injection into semiconductor particles - Importance in photocatalysis- Hydrogen evolution and selective organic photosynthesis catalyzed by zinc sulfide- Photocatalytic organic synthesis by use of semiconductors or dyes- A Hiskia and A Ioannidis Photocatalytic oxidation of organic compounds with heteropoly electrolytes Aspects on photochemical utilization of solar energy- Photoformation of hydrogen in liquid water in the presence of Pt/TiO2 catalyst and organic impurities- Surface properties of catalysts Iron and its oxides: Surface chemistry, photochemistry and catalysis- Photocatalysis over clay supports- Photoreduction and-oxidation of molecular nitrogen on titanium dioxide and titanium containing minerals- Photoassisted reduction of carbon and nitrogen compounds: with semiconductors- Adsorption and desorption processes in photocatalysis- Photo-induced processes at titanium dioxide surfaces- Photolysis of adsorbed phases: Ethanoic acid-insulators and semiconductors systems Influence of acid-base properties- Cadmium sulfide photocatalyzed hydrogen production from aqueous solutions of sulfite- Environmental photochemistry of chlorinated aromatics in aqueous media A review of data- Photodegradation of wastes and pollutants in aquatic environment- Heterogeneous photocatalysis for water purification: Prospects and problems- A Gas Research Institute perspective on inorganic synthesis of gaseous fuels- Putting photocatalysis to work- Panel discussion on the Selective activation and conversion of molecules- Panel discussion on Sensitization and immobilization of catalysts on various supports- Panel discussion on Electrocatalysis and photocatalysis- Final Remarks- Author Index
181 citations
TL;DR: In this paper, the photo-oxidation of toluene on titanium dioxide (TiO2) was studied and the results were discussed in terms of the nature and the amount of the active species formed on the TiO2 surface.
145 citations
TL;DR: In this paper, the photocatalytic hydrogen evolution from aqueous methanol solution over K4Nb6O17 and the photodecomposition of water into H2 and O2 over NiO-K 4Nb 6O17 powder are described.
Abstract: The photocatalytic hydrogen evolution from aqueous methanol solution over K4Nb6O17 and the photodecomposition of water into H2 and O2 over NiO–K4Nb6O17 powder are described.
142 citations
TL;DR: In this paper, the photocatalytic activity of the TiO2/glass beads material has been assessed by two principal light-driven processes: (i) photoreduction of gold(III), and (ii) photodegradation of a chlorinated phenol.
118 citations
93 citations
TL;DR: The electrochemical behavior of the surface species photogenerated at a polycrystalline titanium dioxide film electrode in alkaline solution was investigated by means of cyclic voltammetry as discussed by the authors.
Abstract: The electrochemical behavior of the surface species photogenerated at a polycrystalline titanium dioxide film electrode in alkaline solution was investigated by means of cyclic voltammetry. The obtained results are consistent with the same surface peroxo titanium species being formed when an illuminated TiO/sub 2/ electrode is subjected to an anodic bias or left in open circuit both in the presence and in the absence of oxygen. The decay of these species after the cutoff of illumination was observed to occur relatively slowly, about half of their initial amount being still detectable after 16 h of electrode immersion in sodium hydroxide solution. It was shown that the cathodic reduction of the surface peroxo species, photogenerated at the TiO/sub 2/ electrode, takes place at distinctly more negative potentials than that of dissolved molecular oxygen and that of both preadsorbed and dissolved hydrogen peroxide. The latter species (present mainly as HO/sub 2//sup -/ ions) were also observed to undergo rapid photooxidation at the TiO/sub 2/ photoanode, competing efficiently for positive holes with OH/sup -/ ions. These findings do not support the earlier postulated involvement of the hydrogen peroxide as an intermediate of the photoreaction leading to oxygen evolution. The pathways for the photooxidationmore » reactions at TiO/sub 2/ are briefly discussed in connection with the proposed mechanism of formation of the surface peroxo titanium species. Their role in controlling the surface electron-hole recombination, particularly at dispersed TiO/sub 2/ photocatalysts, is pointed out.« less
77 citations
TL;DR: In this article, the effect of adsorbed water on photocatalytic isomerization has been investigated in the presence of butene and O2 or NO molecules, and it has been shown that the interaction of photo-formed O− species or [Ti3+−O−] pairs results in opening of the C=C bond of butenes.
Abstract: It has been found that UV irradiation of powdered TiO2 catalysts in the presence of butene molecules leads to both cis-trans and double bond shift isomerization reactions with high efficiency. In the photocatalytic isomerization the reactivity of 2-butene is much higher than that of 1-butene, being in contrast to the feature in the thermal isomerization. The addition of O2 or NO molecules leads to the complete inhibition of photocatalytic isomerization of butenes. The effect of adsorbed water on the photocatalytic isomerization has been investigated. From these results together with the ESR measurements under UV irradiation of TiO2 at 77 K in the presence of butene as well as O2 or NO, the following conclusion emerges: The interaction of the photo-formed O− species or [Ti3+–O−] pairs results in opening of the C=C bond of butene, i.e. formation of a radical species, which acts as the intermediate in the photocatalytic isomerization. The O− as well as surface OH− species participates in the hydrogen shift, ...
TL;DR: An efficient photocatalytic dispersion has been developed from CdS and a 0.2 wt.% rhodium(III) salt via photodeposition.
TL;DR: Ammonia was efficiently N-alkylated into tertiary amines by room-temperature photoirradiation at > 300 nm in the presence of platinized titanium dioxide suspended in alcohols, such as methanol, ethanol, and ethylene glycol as discussed by the authors.
01 Jan 1986
TL;DR: The activity of the photocatalysts is significantly dependent on the source of the titanium oxide and the pretreatment conditions employed as discussed by the authors, and the highest activity typically consisted of anatase containing 20-40% of rutile, obtained from iron-doped anatase by a heat-pretreatment.
Abstract: Photoexcitation of titanium dioxide produces reactive centers capable of reducing and possibly oxidizing chemisorbed nitrogen. Activity of the photocatalysts is significantly dependent on the source of the titanium oxide and the pretreatment conditions employed. Photocatalysts with the highest activity typically consisted of anatase containing 20–40% of rutile, obtained from iron-doped anatase by a heat-pretreatment. The photocatalytic reactions of nitrogen can occur in nature on the surface of titanium containing desert sands on exposure to sunlight and thus have ecological significance as parts of the nitrogen cycle.
TL;DR: In this article, the photoredox behavior of copolymers containing covalently bound phthalocyanine moieties was investigated under irradiation with visible light in the presence of a donor and an acceptor.
Abstract: Copolymers containing covalently bound phthalocyanine moieties (4) or tetraphenylporphyrine moieties (5) were prepared by the reaction of partially chloromethylated polystyrene (3) with the low molecular substituted phthalocyanine 1b and tetraphenylporphyrine 2b, respectively. Combined binding of moieties of 1b and 2b yielded polymer 6. The photoredox behavior of 1, 2, 4, 5 and 6 was investigated under irradiation with visible light in the presence of a donor and an acceptor. Mixtures of sensitizers (1 + 2 and 4 + 5) resulted in reduced photocatalytic properties. Only in the case of 6, due to reduced intermolecular interactions, higher yields of photochemical reaction products were obtained.
01 Jan 1986
TL;DR: In this article, a review of the recent results of heterogeneous photocatalysis is presented, including influence of reactant concentration, product inhibition, intermediate formation and disappearance, synthetic vs. solar illumination, and kinetic rate forms, and discuss prospects and problems for future essays.
Abstract: Heterogeneous photocatalysis has demonstrated the complete wet oxidation (mineralization) of a number of common contaminants of water supplies, especially halogenated alkanes, alkenes, and aromatics. We review these recent results, including influence of reactant concentration, product inhibition, intermediate formation and disappearance, synthetic vs. solar illumination, and kinetic rate forms, and discuss prospects and problems for future essays.
TL;DR: In this article, a photocatalytic decomposition of aqueous formic acid was achieved using platinized n-type silicon powder under the conditions that the photocatalyst was spread on the bottom of a reaction cell.
Abstract: Photocatalytic decomposition of aqueous formic acid was successfully achieved by using platinized n-type silicon powder as a photocatalyst under the conditions that the photocatalyst was spread on the bottom of a reaction cell.
TL;DR: In this paper, the photooxidation of D-fructose by M(III) and subsequent reoxidation by atmospheric oxygen was shown to proceed by coupling with an oxidation-reduction cycle involving a metal cation.
Abstract: D-Fructose is susceptible to photochemically-induced oxidation by atmospheric oxygen in the presence of a catalytic amount of iron or manganese cations in a neutral to weakly basic pH range. Metal hydroxide does not precipitate from a solution in this pH range because of the high sequestering ability of D-fructose. Upon irradiation of Pyrex-filtered light, D-fructose degraded into D-erythrose and other fragments. This reaction is shown to proceed by coupling with an oxidation-reduction cycle involving a metal cation, i.e., the photooxidation of D-fructose by M(III) and the subsequent reoxidation of the resultant M(II) by atmospheric oxygen.
01 Jan 1986
TL;DR: In this paper, the effect of illumination on the adsorption equilibrium at semiconductor surfaces (photoadsorption and photodesorption) particularly for the system gaseous oxygen-semiconductor oxides, with a special development on the interest of oxygen isotope exchanges was discussed.
Abstract: In this review, the following topics are discussed: (i)effect of illumination on the adsorption equilibrium at semiconductor surfaces (photoadsorption and photodesorption) particularly for the system gaseous oxygen-semiconductor oxides, with a special development on the interest of oxygen isotope exchanges to assess the lability of adsorbed and surface oxygen atoms; (ii) nature of adsorption sites and of adsorption species, competition between reactants and products derived from kinetic studies of photocatalytic reactions, from ESR spectra and from laser-flash excitation of semiconductor colloids coupled with time-resolved spectroscopies; (iii)evidence for hydrogen spillover between the two components of group VIII metal/titanium dioxide photocatalysts.
TL;DR: A tin-II-coordinated iridium complex catalyst exhibited the highest photoreactivity ever reported for the energy-storing reaction of propan-2-ol dehydrogenation with quantum efficiency and even photo-thermal energy conversion efficiency exceeding unity as discussed by the authors.
Abstract: A tin(II)-co-ordinated iridium complex catalyst exhibited the hightes photoreactivity ever reported for the energy-storing reaction of propan-2-ol dehydrogenation, with quantum efficiency and even ‘photo-thermal energy conversion efficiency’ exceeding unity.
TL;DR: The metathesis of 1-octene using a W(CO)6/hv/CCl4 catalyst system was studied in this paper, where the conversion to 7-tetradecene depends on the initial olefin and catalyst concentrations, and on temperature.
TL;DR: In this article, the photocatalytic activity of CdS and ZnS catalysts for the cis-trans isomerization of 2-butene is investigated.
Abstract: Photocatalytic activity of CdS and ZnS for the cis-trans isomerization of 2-butene is much higher than that of TiO2 and ZnO, though the double bond shift isomerization to 1-butene hardly proceeds in contrast with the case of the oxides The addition of O2 or NO molecules leads to the remarkable inhibition of photocatalyzed isomerization of 2-butene, but not to the complete inhibition Water vapor enhanced the photocatalyzed isomerization From these results together with the ESR measurements before and after UV irradiation of the sulfide catalyst either in the presence or in the absence of butene, the following conclusions emerge: sulfur radicals such as \dotSn, which are produced by the hole trapping by lattice S2− ions and/or sulfur clusters existing in the catalyst inherently, play a significant role in the weakening of the C=C double bond of 2-butene via the interaction with the molecules; the stability of such sulfur radicals results in the much higher photocatalytic activity of CdS and ZnS catalysts
TL;DR: In this article, an oxygen-uptake technique was used to monitor the kinetics of photocatalytic dehydrogenation of propan-2-ol in the presence of the anatase and rutile forms of TiO2.
Abstract: An oxygen-uptake technique has been used to monitor the kinetics of photocatalytic dehydrogenation of propan-2-ol in the presence of the anatase and rutile forms of TiO2. Variation of alcohol concentration showed that surface binding by a non-associated alcohol hydroxy group was necessary before photoconversion into propanone could take place. N.m.r. analysis of solutions of the alcohol in cyclohexane was applied to show that, under the conditions used, the rate of dehydrogenation was proportional to the concentration of free alcohol.
10 Feb 1986
01 Jan 1986
TL;DR: In this article, the practical aspects of photocatalysis as applied to practical problems of some concern and employs semiconductor dispersions of CdS and TiO2 for solving environmental problems caused by discharge of toxic materials into the aquatic and atmospheric ecosystems.
Abstract: This paper emphasizes the practical aspects of photocatalysis as applied to practical problems of some concern and employs semiconductor dispersions of CdS and TiO2. It presents our recent contributions to (i) the photocleavage of hydrogen sulfide, (ii) the treatment of wastes, and (iii) the photoreduction of and recovery of metals on TiO2. It further stresses the point that our present knowledge of photocatalysis and photocatalytic processes can be and must be applied to resolving environmental problems caused by discharge of toxic materials into the aquatic and atmospheric ecosystems. The problems are many; they must be addressed.
TL;DR: In this paper, the photocatalytic reactions of NO at ppm level with O2 were studied in the presence of TiO2 (anatase), PbO, and ZnO using a chemical luminescence NOX analyzer and a second derivative spectrometer.
Abstract: Photocatalytic reactions of NO at ppm level with O2 were studied in the presence of TiO2 (anatase), PbO, and ZnO using a chemical luminescence NOX analyzer and a second derivative spectrometer. The rate of oxidation of NO was very high, e.g. 1930% cm−2 h−1 in a photocatalytic reaction on TiO2 (anatase). Photoadsorption of NOX also took place on these metal oxides.
TL;DR: In this article, an electron transfer mechanism was proposed in which a pair of electron-positive holes generated initially by illumination may transfer an electron to O2 and abstract an electron from diphenylmethane to form O2− and ϕ2CH2+; subsequently, ϕ 2 CH2+ will react with O 2− to give the product.
Abstract: Benzophenone is produced in the photocatalytic oxidation of diphenylmethane in an oxygen saturated TiO2 suspension. The yield is found to increase with increasing solvent polarity. An electron transfer mechanism is proposed in which a pair of electron-positive holes generated initially by illumination may transfer an electron to O2 and abstract an electron from diphenylmethane to form O2− and ϕ2CH2+; subsequently, ϕ2CH2+ will react with O2− to give the product.
TL;DR: In this paper, photo-irradiation of argon-purged aqueous suspension of platinized TiO2 containing t-butyl alcohol at 27 ± 3 °C led to the formation of hydrogen, methane, and ethane in the gas phase, and acetone, t-pentyl alcohol (PntOH), and 2,5-dimethylhexane-2-5-diol (2.5-DH) in the solution phase.
Abstract: Photoirradiation (λex > 300 nm) of argon-purged aqueous suspension of platinized TiO2 containing t-butyl alcohol at 27 ± 3 °C led to the formation of hydrogen, methane, and ethane in the gas phase, and acetone, t-pentyl alcohol (PntOH), and 2,5-dimethylhexane-2,5-diol (2,5-DH) in the solution phase. While TiO2 without Pt showed little activity, the product yields increased linearly upon increasing the amount of Pt loading up to 10 wt%. The increasing concentrations of ButOH up to 0.2M enhanced the product yields, owing to the increase in the amount of adsorbed ButOH on the TiO2 surface. The acetone formation predominated in the presence of either oxygen or silver salt. Product distributions obtained by the γ-irradiation under N2O-saturated conditions and by treatment with Fenton's reagent were similar to that of the photocatalytic reaction by platinized TiO2.