Showing papers by "Michael Grätzel published in 1982"
TL;DR: In this article, a detailed analysis of methods to obtain highly active and selective catalysts, and the performance of bifunctional redox catalysts in cyclic water cleavage systems by visible light is described.
135 citations
TL;DR: In this article, the effect of RuO2 is attributed to catalysis of hole transfer from the valence band of CdS to H2S or sulfide ion in solution.
Abstract: Illumination of US-dispersions by visible light in solutions containing H2S or sulfide ions leads to efficient generation of hydrogen and sulfur. Very small quantities of RuO2 deposited on the CdS-particles improve markedly the quantum yield of H2-formation for which the optimum value obtained so far is ϕ = 0.35 ± 0.1. The effect of RuO2 is attributed to catalysis of hole transfer from the valence band of CdS to H2S or sulfide in solution.
130 citations
TL;DR: Aqueous sols of TiO2 (anatase, particle radius 25 A) were excited with (347.1 nm)-laser light and the reaction of valence-band holes with halide ions (X = I−, Br−, Cl−) was investigated as discussed by the authors.
Abstract: Aqueous sols of TiO2 (anatase, particle radius 25 A) were excited with (347.1 nm)-laser light and the reaction of valence-band holes with halide ions (X = I−, Br−, Cl−) was investigated. Hole transfer takes place within the duration of the (10 ns)-laser pulse and results in the formation of anion radicals according to the sequence:
The quantum yield of X increases in the order Cl < Br < I, attaining 0.8 for I at pH 1. It is affected by pH, halide concentration and the presence of a protective agent for the sol.
RuO2 deposited onto TiO2 enhances markedly Cl and Br -formation, but has no effect on the yield of I.
Laser-photolysis investigation of halide oxidation were also carried out with colloidal Fe2O3 (particle radius 600 A). For I2−formation, the quantum yield exceeds 0.9 indicating almost quantitative hole scavenging by iodide.
97 citations
TL;DR: Bis(carboxycyclopentadienyl) cobalt Co(C5H4CO2H)2+(1) and the cobalt(III) sepulchrate Co(sep)3-9(2) produce hydrogen from water after single elecron reduction in an electrochemical process, and act as electron relays in photochemical hydrogen generating systems as discussed by the authors.
Abstract: Bis(carboxycyclopentadienyl) cobalt Co(C5H4CO2H)2+(1) and the cobalt(III) sepulchrate Co(sep)3– 9(2) produce hydrogen from water after single elecron reduction in an electrochemical process, and act as electron relays in photochemical hydrogen generating systems.
41 citations
24 citations
TL;DR: In this paper, the authors deal with artificial (non-biological) systems that achieve fuel generation by visible light and discuss intrinsic features of light driven redox processes in organized assemblies such as surfactant micelles and colloidal semiconductors.
Abstract: This article deals with artificial (non biological) systems that achieve fuel generation by visible light. Intrinsic features of light driven redox processes in organized assemblies such as surfactant micelles and colloidal semiconductors are discussed. When coupled with suitable highly active redox catalysts these devices can be employed to accomplish cleavage of water or hydrogen sulfide by visible light.
22 citations
TL;DR: In this article, four electron carriers (two zwitterionic bipyridyls, dicarboxyl colbalticinium and sodium metatungstate), which are negatively charged in their reduced form, have been tested as photo-system acceptors and as mediators of H2 evolution.
Abstract: Four novel electron carriers (two zwitterionic bipyridyls, dicarboxyl colbalticinium and sodium metatungstate), which are negatively charged in their reduced form, have been tested as photo-system I acceptors and as mediators of H2 evolution. Measurements of O2 uptake, anaerobic photoreduction rates and stationary concentrations of reduced species under continuous illumination indicate that Coulombic interactions control the electron transfer between the photosynthetic membrane and the mediators. Both rates of forward transfer and back reaction (electron cycling) seem to depend on the charge of the electron carrier. The low concentration of anionic species in the diffuse layer associated with the membrane could explain our results. Hydrogen evolution rates obtained with these four mediators used as electron relays between the photosynthetic membrane and colloidal platinum catalyst are higher than with methylviologen. This improvement of the conversion efficiency parallels the high steady state accumulation of reduced carriers favoured by their negative charge. It is also shown that these synthetic mediators, except metatungstate, are able to evolve hydrogen with an hydrogenase isolated from Desulfovibrio desulfuricans.
13 citations
TL;DR: In this paper, a brief overview of these artificial systems and some basic principles of their operation is given. But the main focus of this paper is on the basic principles and their operation.
Abstract: Presently endeavors are being undertaken to design systems capable of converting solar radiation into fuels. These efforts are timely and mandatory in order to reduce our dependence on fossil energy reserves. Recently there has been an explosion of information on this subject1–13 and a multitude of processes are under investigation which attempt to mimic photosynthesis. The present article gives a brief overview over these artificial systems and explains some basic principles of their operation.
10 citations
TL;DR: The LPI-ARTICLE-1982-031 paper as discussed by the authors was the first publication of the Web of Science Record created on 2006-02-21, modified on 2017-05-12.
Abstract: Reference LPI-ARTICLE-1982-031doi:10.1002/hlca.19820650820View record in Web of Science Record created on 2006-02-21, modified on 2017-05-12
8 citations
TL;DR: In this paper, the authors reported the generation of Cl2 when aqueous dispersions of WO3 solutions of NaCl are irradiated in the visible The rate of Cl 2 evolution is dependent on the amount of catalyst, pH of solution, concentration of NCl used, intensity of light and concentration of the oxidant (O2).
Abstract: This study reports the generation of Cl2 when aqueous dispersions of WO3 solutions of NaCl are irradiated in the visible The rate of Cl2 evolution is dependent on the amount of catalyst, pH of solution, concentration of NaCl used, intensity of light and concentration of the oxidant (O2) present WO3 is also photoactive in LiCl solutions and O2 reduction was also observed in this case Light promotes the transfer of an electron from Cl– to O2 in a reaction that is thermodynamically uphill
5 citations
TL;DR: Polycrystalline WO3electrodes, when illuminated with visible light in acid hydrogen sulphate solutions, have been shown to produce peroxodisulphate with 85% current efficiency as discussed by the authors.
Abstract: Polycrystalline WO3electrodes, When illuminated with visible light in acid hydrogen sulphate solutions, have been shown to produce peroxodisulphate with 85% current efficiency.
01 Feb 1982
TL;DR: In this article, the authors present a Web of Science Record created on 2006-02-21, modified on 2017-05-12 for the LPI-ARTICLE-1982-020.
Abstract: Reference LPI-ARTICLE-1982-020View record in Web of Science Record created on 2006-02-21, modified on 2017-05-12