Joost Manassen
Weizmann Institute of Science
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Featured researches published by Joost Manassen.
Nature | 1976
Gary Hodes; Joost Manassen; David Cahen
WE report here on a major improvement in the conversion efficiency of corrosion-free photoelectrochemical cells (PECs) and on a novel extension of such cells which allows the storage of part or all of the converted energy in situ for subsequent use.
Journal of The Electrochemical Society | 1980
Gary Hodes; Joost Manassen; David Cahen
Porous electrocatalytic electrodes for the polysulfide redox system, containing one of various metallic sulfides (especially of Co, Cu, Pb) are described. Emphasis is placed on their use as counterelectrodes in photoelectrochemical cells employing polysulfide electrolytes. Their activity is measured as a function of electrolyte temperature and composition. The ratio of S to S2−, and through it the local redox potential of the solution, is shown to be an important factor controlling electrode activity. The short and long term stability of the electrodes, as cathodes, is discussed, and it is shown that, when used in conjunction with photoanodes, and may poison the photoelectrode surface, thereby reducing total cell efficiency.
Solar Energy Materials | 1983
B. Aurian-Blajeni; M. Halmann; Joost Manassen
Abstract The photoelectrochemical reduction of aqueous carbon dioxide was carried out using single crystal p-gallium phosphide and p-gallium arsenide as photocathodes. The organic products measured were mainly formic acid, but also formaldehyde and methanol. The effect of carbon dioxide pressure on the current-potential relationships and on yields of organic reduction products was studied using a photoelectrochemical autoclave, fitted with a quartz window. Highest Faradaic yield of reduction products, 80%, was obtained with a p-GaP cathode at a cathodic bias of -1.00 V (vs. a standard silver electrode), in a medium initially 0.5 M Na2CO3, under 8.5 atm pressure of CO2, a cation exchange diaphragm and a platinum counterelectrode, under illumination with a 150 W Xe lamp.
Archive | 1966
Herman Pines; Joost Manassen
Publisher Summary The mechanism of dehydration of alcohols over “acidic” and “nonacidic” alumina is the same. In the presence of the “acidic” alumina, the readsorption of the dehydrated product can occur, leading to either double bond migration or skeletal isomerization, depending on the strength of the acid sites, the structure of the olefins produced, and the experimental conditions. The dehydration of tertiary alcohols over aluminas can be interpreted by a carbonium ion mechanism. Experimental evidence demonstrates that secondary and primary alcohols are dehydrated by a concerted mechanism, whereby both the intrinsic acid and base sites of the alumina participate. The steric course of the reaction proves that the dehydration of alkylcyclohexanols proceeds via a trans elimination. There is a strong parallel between elimination reactions in solution and the dehydration of alcohols over alumina. The trans elimination reactions and the anchimeric assistance of alcohols over aluminas suggest that the dehydration must occur within either the submicroscopical pores, or crevices, or channels of the aluminas. The aluminas therefore, must surround the alcohol molecules providing acid sites to act as proton donors or electron acceptors and basic sites to act as proton acceptors or electron donors.
Journal of The Electrochemical Society | 1977
Joost Manassen; Gary Hodes; David Cahen
The photoelectrochemical cell (PEC) furnishes an alternative to the commercially available photovoltaic cells for the direct conversion of sunlight into electrical energy. It has the distinct advantage over a photovoltaic cell in that storage of the converted energy is possible in situ. Some general principles connected with storage in a PEC are discussed, and experimental evidence is given that, after due development, this mode may be able to compete with the combination photovoltaic cell/storage battery.
Thin Solid Films | 1982
Gary Hodes; Joost Manassen; Sorina Neagu; David Cahen; Y. Mirovsky
Abstract CdSe and Cd(Se, Te) alloy layers were electroplated onto titanium substrates from both acid and alkaline baths. When annealed, these layers show good photoelectrode behaviour in a polysulphide electrolyte with high quantum efficiencies and stability. Donor densities are found to be in the range of 10 14 –10 15 cm -3 . Scanning electron microscopy studies show the layers to have a very irregular morphology and generally to be composed of elongated spherical particles. Annealing conditions can be chosen such that the layers are of cubic or hexagonal structure.
Applied Physics Letters | 1985
Stuart Licht; Reshef Tenne; Geulah Dagan; Gary Hodes; Joost Manassen; David Cahen; R. Triboulet; Jacques Rioux; Claude Lévy-Clément
High efficiency (12.7%) CdSe0.68Te0.32/cesium polysulfide photoelectrochemical cells are demonstrated in this work. Crystals of the ternary alloy Cd(Se, Te) of type n type were synthesized by the traveling heater method. The nature of the polysulfide electrolyte, based on Cs polysulfide without excess hydroxide and containing small amounts of copper ions, is shown to be of particular importance in determining the cell efficiency. Reasonable output stability of the cell was obtained under accelerated tests.
Journal of Catalysis | 1970
Joost Manassen; Amiram Bar-Ilan
Abstract The catalytic activity of tetraphenyl porphyrin and phthalocyanine complexes for the heterogeneous dehydrogenation of cyclohexadiene in the gas phase, using nitro-benzene as the oxidizing agent, was measured. A general correlation of catalytic activity with polarographically measured first oxidation potentials was found. By controlled potential electrolysis, coulometry and EPR measurements, the mode of oxidation of these complexes in solution was ascertained. The first oxidation of Fe 2+ and Co 2+ tetraphenyl porphyrin appeared to be at the central metal atom, while the Zn 2+ and Cu 2+ complexes gave ligand oxidation. For the Ni 2+ complex the potentials for central metal atom oxidation and ligand oxidation were very close together. Therefore, these complexes were capable of two kinds of redox processes, either valency change of the central metal atom (Fe 2+ , Co 2+ ) or ligand oxidation/reduction (Cu 2+ , Zn 2+ ) or both (Ni 2+ ). By comparing these principles with results obtained earlier on the catalytic activity of these complexes for cumene oxidation, this difference in redox mechanism could be correlated with the catalytic activity of the complexes in question.
Journal of Applied Electrochemistry | 1977
Gary Hodes; Joost Manassen; David Cahen
Electrodes for the sulphide/sulphur (polysulphide) redox system are described which show low polarization when operated under conditions to be expected in a practical photo-electrochemical cell (P. E. C.)-These electrodes are composed of Teflon-bonded high surface area carbon, loaded with electrocatalysts, the best results having been obtained using cobalt as electrocatalyst.
Photochemistry and Photobiology | 1982
B. Aurian-Blajeni; M. Halmann; Joost Manassen
Abstract— Free radical intermediates appearing during illumination of aqueous suspensions of tungsten oxide were detected by electron spin resonance using the technique of spin trapping. Solutions irradiated contained methanol, formaldehyde, sodium formate and sodium hydrogen carbonate. Signals assigned to the spin adducts of the •H, •OH, •CO2‐ and •CH2OH radicals were found.