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Electrolyte Interface (electrolyte + interface)
Selected AbstractsHigh Molar Extinction Coefficient Ion-Coordinating Ruthenium Sensitizer for Efficient and Stable Mesoscopic Dye-Sensitized Solar Cells,ADVANCED FUNCTIONAL MATERIALS, Issue 1 2007D. Kuang Abstract Ru(4,4-dicarboxylic acid-2,2,-bipyridine) (4,4,-bis(2-(4-(1,4,7,10-tetraoxyundecyl)phenyl)ethenyl)-2,2,-bipyridine) (NCS)2, a new high molar extinction coefficient ion-coordinating ruthenium sensitizer was synthesized and characterized using 1H,NMR, Fourier transform IR (FTIR), and UV/vis spectroscopies and cyclic voltammetry. Using this sensitizer in combination with a nonvolatile organic-solvent-based electrolyte, we obtain a photovoltaic efficiency of 8.4,% under standard global AM,1.5 sunlight. These devices exhibit excellent stability when subjected to continuous thermal stress at 80,°C or light soaking at 60,°C for 1000,h. An electrochemical impedance spectroscopy study revealed that device stability is maintained by stabilizing the TiO2/dye/electrolyte and Pt/electrolyte interface during the aging process. The influence of Li+ present in the electrolyte on the device photovoltaic parameters was studied, and the FTIR spectral and photovoltage transient study showed that Li+ coordinates to the triethyleneoxide methylether side chains on the K60 sensitizer molecules. [source] Investigation of p-type macroporous silicon formationPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 8 2005C. Lévy-Clément Abstract Nanopores and macropores can be formed electrochemically on p-type silicon depending on the silicon resistivity and composition of the electrolyte. In order to understand if the structural dimensionality of the porous p-type Si, either nanopore or macropore formation, depends on the electrochemical process at the Si/electrolyte interface, in situ pulsed surface photovoltage (SPV) and photoluminescence (PL) measurements have been undertaken. The SPV and PL studies have been made as a function of the applied current density as well as the electrolyte composition (aqueous or in presence of organic solvent) and the silicon doping density. Main results show that the Si surface is well passivated with preferential formation of ionic species and the Si band bending is around 100 mV, during porous Si formation. It varies slightly with the doping density, but is not affected by the composition of the electrolyte (HF/water and HF/organic solvent). This demonstrates that the chemistry of the electrolyte plays a major role in the formation of macroporous and nanoporous Si, but has still to be determined. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Electrochemical stabilization of crystalline silicon with aromatic self-assembled monolayers in aqueous electrolytesPHYSICA STATUS SOLIDI (B) BASIC SOLID STATE PHYSICS, Issue 14 2005Murat Tutus Abstract We report stable chemical engineering of hydrogen-terminated Si[111] surfaces in aqueous electrolytes by electrochemical grafting of aromatic monolayers. The topography and free energy of the engineered surface obtained from AFM and contact angle measurements confirmed homogeneous coating of the surface with a monolayer. Grafting of monolayers actually resulted in a clear suppression of the surface defect densities, demonstrated by photoluminescence lifetime. Changes in the surface chemical identities after grafting and post-treatments were followed by X-ray photoelectron spectroscopy (XPS). The electrochemical stability in aqueous electrolytes was assessed by impedance spectroscopy, revealing an improved stabilization of the Si/electrolyte interface by the grafted monomolecular film. This protocol was further applied for another aromatic compound, where the impact of 4-substituent functions could clearly be detected by photovoltage measurements. The chemical and electrochemical stability achieved here is promising for the successive deposition of biocompatible polymer films and lipid membranes. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Numerical analysis of thermal and electrochemical phenomena for anode supported microtubular SOFCAICHE JOURNAL, Issue 3 2009Daan Cui Abstract A 2D model considering momentum, heat/species transport and electrochemical phenomena, has been proposed for tubular solid oxide fuel cell. The model was validated using experimental polarization curves and the good agreement with the experimental data was attained. The temperature distributions show that temperature varies severely at the tube inlet than at the tube outlet. The heat generation and transfer mechanisms in electrodes, electrolyte and electrochemical reaction interface were investigated. The results show that the overall electrochemical reaction heat is produced at cathode/electrolyte interface, and a small portion of the heat is consumed at anode/electrolyte interface. The heat produced at cathode/electrolyte interface is about five times as much as that consumed at anode/electrolyte interface. Overwhelming part of the heat transfer between cell and outside occurs at cathode external surface. Most current flow goes into anode from a very small area where the current collectors locates. © 2009 American Institute of Chemical Engineers AIChE J, 2009 [source] The Influence of Doping Levels and Surface Termination on the Electrochemistry of Polycrystalline DiamondELECTROANALYSIS, Issue 6 2004Matthew Abstract The influence of surface chemistry and boron doping density on the redox chemistry of Fe(CN) at CVD polycrystalline diamond electrodes is considered. It is demonstrated that for this couple both the doping density and the surface chemistry are important in determining the rate of charge transfer at the electrode/electrolyte interface. For hydrogen terminated CVD diamond metallic electrochemical behavior is always observed, even at boron doping densities as low as 7×1018,cm,3. In contrast, the electrochemical behavior of oxygen terminated CVD diamond varies with doping density, a metallic response being observed at high doping density and semiconductor behavior at low doping density. It is shown that the results attained may be explained by a surface state mediated charge transfer mechanism, thus demonstrating the importance of controlling surface chemistry in electroanalytical applications of diamond. [source] Preparation of lithium indium oxide via a rheological phase route and its electrochemical characteristics in LiOH and Li2SO4 solutionsPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 1 2010Guo-Qing Zhang Abstract Submicrometer-sized lithium indium oxide (LiInO2) powder via a rheological phase method using trilithium citrate tetra hydrate (C6H5Li3O7,·,4H2O) and indium oxide (In2O3) has been prepared in this work for the first time. The optimal pyrolyzing temperature range to prepare crystalline LiInO2 is between 650 and 900,°C, which was confirmed by thermal gravimetric and differential thermogravimetric analysis of the precursor and X-ray diffraction analysis. The pure phase LiInO2 sample obtained has a uniform particle morphology and submicrosize, which was observed by scanning electron microscopy. The electrochemical studies show that a new pair of cathodic and anodic peaks at 0.23 and 0.38,V (vs. saturated calomel electrode) was obviously observed from the cyclic voltammetry curve of LiInO2 in 1,M LiOH solution, indicating a battery characteristic of the material in this electrolyte. While in 1,M Li2SO4 solution, the sample presents a supercapacitive characteristic within the same potential range. The reasons for different electrochemical behaviors in these two electrolytes can be attributed to the fact that the reaction of lithium ion insertion/extraction into/out of a LiInO2 electrode takes place in the bulk material in LiOH electrolyte solution, whereas it takes place on the electrode/electrolyte interface for Li2SO4 electrolyte case. [source] Amperometry of Heparin Polyion Using a Rotating Disk Electrode Coated with a Plasticized PVC MembraneELECTROANALYSIS, Issue 2 2006Jan Langmaier Abstract Electrochemical method of detection of heparin polyion was developed based on voltammetry of heparin on a rotating glassy carbon (GC) electrode coated with a plasticized PVC membrane. The membrane was deposited on the GC disk by spin-coating technique using a mixture of solutions of PVC in tetrahydrofuran, and 1,1,-dimethylferrocene (DMFc) and hexadecyltrimethylammonium tetrakis(4-chlorophenyl)borate (HTMATPBCl) in o -nitrophenyl octyl ether. UV/vis reflection spectrometry was used to evaluate the membrane thickness, which exhibits a linear correlation with the membrane resistance measured by impedance spectroscopy. It is shown that this electrode can be used for amperometric or coulometric detection of heparin in aqueous samples of medically relevant concentrations (1,10,U mL,1), with a detection limit of 1.4,U mL,1. Evidence is provided indicating that the current determining step is the reversible adsorption of the ion-pair of heparin polyion with HTMA+ cation at the membrane/aqueous electrolyte interface, which is driven by oxidation of DMFc at the GC/membrane interface. [source] Solar Cells by Design: Photoelectrochemistry of TiO2 Nanorod Arrays Decorated with CdSeADVANCED FUNCTIONAL MATERIALS, Issue 12 2010Jin Ho Bang Abstract One-dimensional (1D) nanostructures of TiO2 are grown directly on transparent, conductive glass substrate using hydrothermal/solvothermal methods. When employed as a photoanode in photoelectrochemical cells, the vertically aligned TiO2 nanorod array exhibits slower charge recombination at electrolyte interface as compared to mesoscopic TiO2 particulate film. Electrochemical deposition of CdSe onto TiO2 nanorod array is carried out to extend absorption into visible light region. The role of CdSe-sensitized, 1D rutile TiO2 architecture in the solar cell design is discussed. [source] Two-phase flow electrosynthesis: Comparing N -octyl-2-pyrrolidone,aqueous and acetonitrile,aqueous three-phase boundary reactionsJOURNAL OF PHYSICAL ORGANIC CHEMISTRY, Issue 1 2009Stuart M. MacDonald Abstract A microfluidic double channel device is employed to study reactions at flowing liquid,liquid junctions in contact with a boron-doped diamond (BDD) working electrode. The rectangular flow cell is calibrated for both single-phase liquid flow and biphasic liquid,liquid flow for the case of (i) the immiscible N -octyl-2-pyrrolidone (NOP),aqueous electrolyte system and (ii) the immiscible acetonitrile,aqueous electrolyte system. The influence of flow speed and liquid viscosity on the position of the phase boundary and mass transport-controlled limiting currents are examined. In contrast to the NOP,aqueous electrolyte case, the acetonitrile,aqueous electrolyte system is shown to behave close to ideal without ,undercutting' of the organic phase under the aqueous phase. The limiting current for three-phase boundary reactions is only weakly dependent on flow rate but directly proportional to the concentration and the diffusion coefficient in the organic phase. Acetonitrile as a commonly employed synthetic solvent is shown here to allow effective three-phase boundary processes to occur due to a lower viscosity enabling faster diffusion. N -butylferrocene is shown to be oxidised at the acetonitrile,aqueous electrolyte interface about 12 times faster when compared with the same process at the NOP,aqueous electrolyte interface. Conditions suitable for clean two-phase electrosynthetic processes without intentionally added supporting electrolyte in the organic phase are proposed. Copyright © 2008 John Wiley & Sons, Ltd. [source] Advances in Photoelectrocatalysis with Nanotopographical PhotoelectrodesCHEMPHYSCHEM, Issue 8 2010A. G. Muñoz Dr. Abstract The design of photoelectrodes for high efficiency solar fuel energy conversion devices is based on the search for adequate surface conditioning to achieve efficient light harvesting, stability, minimized surface recombination losses and high electron-transfer rates at the electrolyte interface. An overview on established and novel approaches is given. A recent viable solution is provided by electroplating of nanoscale catalytic metals on passivated semiconductor surfaces, thereby forming reactive centers and avoiding contact between the semiconductor surface and the electrolyte. At these nano-dimensioned Schottky-type junctions, light-induced excess minority carriers are scavenged and transferred to the electrolyte. Various possible device configurations are outlined and envisaged systems for hydrogen or oxygen evolution and carbon dioxide reduction are presented. The role of ultrathin passivating films is emphasized and methods to fabricate open as well as compact conformal films are described. [source] Graphene Solution-Gated Field-Effect Transistor Array for Sensing ApplicationsADVANCED FUNCTIONAL MATERIALS, Issue 18 2010Markus Dankerl Abstract Graphene, with its unique combination of physical and electronic properties, holds great promise for biosensor and bioelectronic applications. In this respect, the development of graphene solution-gated field-effect transistor (SGFET) arrays capable of operation in aqueous environments will establish the real potential of graphene in this rapidly emerging field. Here, we report on a facile route for the scalable fabrication of such graphene transistor arrays and provide a comprehensive characterization of their operation in aqueous electrolytes. An on-chip structure for Hall-effect measurements allows the direct determination of charge carrier concentrations and mobilities under electrolyte gate control. The effect of the solution-gate potential on the electronic properties of graphene is explained using a model that considers the microscopic structure of water at the graphene/electrolyte interface. The graphene SGFETs exhibit a high transconductance and correspondingly high sensitivity, together with an effective gate noise as low as tens of ,V. Our study demonstrates that graphene SGFETs, with their facile technology, high transconductance, and low noise promise to far outperform state-of-the-art Si-based devices for biosensor and bioelectronic applications. [source] Anodic oxides on a beta type Nb,Ti alloy and their characterization by electrochemical impedance spectroscopyPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 4 2010Michael Teka Woldemedhin Abstract Anodic oxides were grown on the surface of an electropolished (Ti,30,at% Nb) beta-titanium (,-Ti) alloy by cyclic voltammetry. The scan rate was 100,mV,s,1 between 0 and 8,V in increments of l,V in an acetate buffer of pH 6.0. Electrochemical impedance spectroscopy was carried out right after each anodic oxide growth increment to study the electronic properties of the oxide/electrolyte interface in a wide frequency range from 100,kHz to 10,MHz with an AC perturbation voltage of 10,mV. A film formation factor of 2.4,nm,V,1 was found and a relative permittivity number (dielectric constant) of 42.4 was determined for the oxide film formed. Mott,Schottky analysis on a potentiostatically formed 7,nm thick oxide film was performed to assess the semiconducting properties of the mixed anodic oxide grown on the alloy. A flat band potential of ,0.47,V (standard hydrogen electrode, SHE) was determined, connected to a donor density of 8.2,×,1017,cm,3. ,-Ti being highly isotropic in terms of mechanical properties should be superior to the stiffer ,-Ti compound. Its application, however, requires a passivation behaviour comparable or better than ,-Ti which in fact is found. [source] | |||||||||||||