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Showing papers by "Michael Grätzel published in 1990"


Journal ArticleDOI
TL;DR: A series of CN-bridged trinuclear Ru complexes of the general structure [RuL2(μ-(CN)Ru(CN)L2′)2] have been synthesized, and their spectral and electrochemical properties investigated as mentioned in this paper.
Abstract: A series of CN-bridged trinuclear Ru complexes of the general structure [RuL2(μ-(CN)Ru(CN)L2′)2] where L is 2,2′-bipyridine-4,4′-dicarboxylic acid and L′ is 2,2′-bipyridine (1)2,2′-bipyridine-4,4′-dicarboxylic acid (2), 4,4′-dimethyl-2,2′-bipyridine (3), 4,4′-diphenyl-2,2′-bipyridine (4), 1,10-phenanthroline (5), and bathophenanthrolinedisulfonic acid (6) have been synthesized, and their spectral and electrochemical properties investigated. The two carboxylic functions on the 2,2′-bipyridine ligand L serve as interlocking groups through which the dye is attached at the surface of TiO2 films having a specific surface texture. The role of these interlocking groups is to provide strong electronic coupling between the π* orbital of the 2,2′-bipyridine and the 3d-wave-function manifold of the conduction band of the TiO2, allowing the charge injection to proceed at quantum yields close to 100 %. The charge injection and recombination dynamics have been studied with colloidal TiO2, using laser photolysis technique in conjunction with time-resolved optical spectroscopy. Photocurrent action spectra obtained from photo-electrochemical experiments with these trinuclear complexes cover a very broad range in the visible, making them attractive candidates for solar light harvesting. Monochromatic incident photon-to-current conversion efficiencies are strikingly high exceeding 80% in some cases. Performance characteristics of regenerative cells operating with these trinuclear complexes and ethanolic triiodide/iodide redox electrolyte have been investigated. Optimal results were obtained with complex 1 which gave a fill factor of 75 % and a power conversion efficiency of 11.3% at 520 nm.

209 citations


Journal ArticleDOI
TL;DR: In this paper, a mechanism of degradative oxidation on the TiO2 particles involving epoxidation by surface peroxo species and direct hole oxidation is proposed, which enhances dramatically the rate of catalytic activity by inhibition of the electron and hole back-reaction as well as direct oxidation of the substrate species by the strong oxidants themselves.

125 citations


Journal ArticleDOI
TL;DR: In this paper, a K + sensor based on the admittance change of synthetic bilayer membranes supported on Si/SiO 2 electrodes is reported, which is formed on thermally oxidized silicon derivatized with (3,3'-dimethylbutyl)dimethyl(dimethylamino)silane by self-assembly of distearoylphosphatidylcholine and tetradecyl-18-crown-6 from ethanol+H 2 O solutions or by the transfer of a compressed mixed monolayer film from a Langmuir trough

45 citations


Journal ArticleDOI
TL;DR: A photoelectrochemical cell was set up with the PS II-covered TiO 2 as the anode, a platinum cathode as the counterelectrode and a saturated calomel electrode (SCE) as reference electrode, with 50 mM NaCl as electrolyte as mentioned in this paper.
Abstract: Oxygen-evolving photosystem II (PS II) particles prepared from spinach chloroplasts were deposited on the surfaces of different types of dye-derivatized polycrystalline TiO 2 electrodes. A photoelectrochemical cell was set up with the PS II-covered TiO 2 as the anode, a platinum cathode as the counterelectrode and a saturated calomel electrode (SCE) as reference electrode, with 50 mM NaCl as electrolyte. The cell was connected to a potentiostat maintained at 0.2 V vs. SCE. On irradiation of the cell with white light, in the presence of a PS II electron acceptor (benzoquinone derivatives), a steady photocurrent was observed. This photocurrent production was completely inhibited by 3-(3′,4′-dichlorophenyl)-1,1′-dimethylurea (DCMU), a photosynthetic oxygen evolution inhibitor; there was no decrease in the photocurrent response on addition of DCMU when no PS II was deposited on the TiO 2 or when the TiO 2 was covered with heat-inactivated PS II. Thus the source of electrons for the DCMU-sensitive photocurrent is water photolysis. The maximum monochromatic incident photon to current conversion efficiency observed was 12%. Photocurrents up to 35 μA cm −2 of electrode surface and 10 mA mg −1 of chlorophyll were obtained on illumination with white light of 35 mW cm −2 intensity. Approximately 20% of the photosynthetic electron transport rate of the PS II particles (measured as oxygen evolution) was manifested as photocurrent.

34 citations


Journal ArticleDOI
TL;DR: In this article, a P25-supported Ru catalysts are used for NO-CO reaction at temperatures as low as ambient in a batch reactor, where the reaction products are CO2, N2O, and N2.

24 citations


Journal ArticleDOI
TL;DR: In this article, the authors used supported palladium oxide catalysts to convert CH4 to C2H6, CO, CO 2, CO2, H2 and H2O at temperatures below 400 °C.
Abstract: Supported palladium oxide catalysts are able to convert CH4 to C2H6, CO, CO2, H2 and H2O at temperatures ⩾315 °C. Catalysts did not show any support effect when TiO2, Al2O3, ZrO2, La2O3 and MgO were used as supports. With sequential O2 pulsing the catalyst showed long term activity when used at temperatures below 400 °C. Addition of Pt increased selectivity whereas with Ga it decreased. Results indicate participation of lattice O2 from catalyst in the reaction pathway.

22 citations


Journal ArticleDOI
TL;DR: The electropolymerisation of aniline is accelerated by the presence of sodium polyvinyl sulphonate in the monomer solution and can be initiated at a less anodic potential than in its absence while the densely compact structure of the polymer is retained as discussed by the authors.
Abstract: The electropolymerisation of aniline is accelerated by the presence of sodium polyvinyl sulphonate in the monomer solution and can be initiated at a less anodic potential than in its absence while the densely compact structure of the polymer is retained.

20 citations


Journal ArticleDOI
TL;DR: In this article, deviations from classical Cottrell behaviour have been observed for the time dependence of the current transient following a potential step at the interface between a rough textured semiconductor surface and a solution of an electroactive species, when that potential step causes the interface to pass from a blocking to a charge transfer state.

16 citations


Journal ArticleDOI
TL;DR: In this paper, an Oxidative coupling of methane with good C2+ selectivity and yield was achieved over a variety of molybdate compounds without losing their catalytic activity during 200 to 280 h of study.
Abstract: Oxidative coupling of methane with good C2+ selectivity and yield was achieved over a variety of molybdate compounds without losing their catalytic activity during 200 to 280 h of study.

10 citations


Journal ArticleDOI
TL;DR: In this article, the authors investigated whether MoS{sub 2}/Al-sub 2]O{sub O{sub 3} directly catalyzes the methanation of CO with S, without added sulfur impurities, and the efficiency of the reaction, the effect of temperature and the characteristics of the catalyst.

9 citations


Journal ArticleDOI
TL;DR: In this paper, the TView record in Web of Science Record created on 2006-02-21, modified on 2017-05-12 has been broken for the first time.

Journal ArticleDOI
TL;DR: Palladium oxide and TiO2-supported palladium oxide, prepared by the deposition-precipitation technique were reduced using CH4 at temperatures greater than 300 °C as mentioned in this paper.
Abstract: Palladium oxide and TiO2-supported palladium oxide, prepared by the deposition–precipitation technique were reduced using CH4 at temperatures greater than 300 °C. Other oxides, such as PtO2, PtOx/TiO2, Co3O4/TiO2 and Fe2O3 were also used. These oxides showed varying degrees of reduction. During reduction, CH4 was oxidised and the reaction products (CO, CO2, H2O(g) and H2) were identified by gas chromatography. The results indicate that CH4 is capable of causing deep-level redox reactions in the bulk by diffusing through the catalyst surface. Palladium and platinum oxides were found to be suitable materials for such reduction treatments. The most active catalysts were characterized by diffuse reflectance spectroscopy (DRS), elemental analysis, X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). Formation of Pd with different oxidation states was noted on the surface of the reduced catalyst. Unlike Pd-based catalysts, PtO2/TiO2 samples showed a stabilisation of Ti3+ on the catalyst surface.

Book ChapterDOI
01 Jan 1990
TL;DR: In this paper, a photoelectrochemical cell was shown to produce continuous photocurrents in the presence of a reductant which would reduce the oxidised dye in the conduction band of the anode.
Abstract: During photosynthesis light energy absorbed by the photosynthetic reaction centres is converted to chemical energy in the form of ATP and NAD(P)H2: in photoelectrochemical cells light energy absorbed by a sensitized electrode is converted to electrical or chemical energy. For example, if a TiO2 semiconductor electrode (anode) coated with a dye (to improve the visible light sensitivity of the electrode) is irradiated with visible light the dye molecules get excited and inject electrons into the conduction band of the TiO2. These electrons can be directed towards a counter electrode (cathode) to generate a photocurrent — continuous photocurrent is produced in the presence of a reductant which would reduce the oxidised dye (1).