Photoelectrochemistry of Culn11S17

Polycrystalline samples of Culn₁₁S₁₇ have been prepared by the homogeneous precipitation technique. The electron probe microanalyses (EPMA) have shown the presence of excess sulphur with as-precipitated samples, which has been considerably reduced by subsequent annealing. From the reflectance measurements, the band gap has been determined to be 1.45eV. The photoelectrochemical behaviour of n-Culn₁₁S₁₇ has been studied in different redox electrolytes, namely, polysulphide, polyiodide, and ferro/ferricyanide, and the best photoresponse was observed with the polysulphide redox system. Photoetching in a poly-sulphide electrolyte at a strong anodic bias highly improves the photoresponse of this material. It has also been shown that our n-Culn₁₁S₁₇ photoanode in electrochemical photovoltaic cell has a good stability at working conditions in a polysulphide solution. Finally, the future perspectives of the material have been briefly discussed.     

Electrochemical solar cell based on a sprayed CdS film photoanode

Electrochemical studies of the CdS film deposited onto a transparent conductive SnO₂-coated glass slide by chemical spray deposition were performed in aqueous polysulphide solutions and the output characteristics of the electrochemical photocell (sprayed CdS film/polysulphide electrolyte/Pt) were measured. It was proved to be possible to construct a regenerative photocell free from the light losses through the polysulphide solution path by illuminating the CdS film anode through the SnO₂-coated glass. Quantum yield and the maximum energy conversion efficiency of this photocell for monochromatic excitation of 480 nm were about 8% and 0.5%, respectively. It is concluded that the poorer quantum yield of this photocell employing CdS film than that of a photocell employing single crystal CdS can be attributed to the existence of lattice imperfections in the film.     

Permeability of poly-L-methionine membrane and its oxidized membrane to water vapor

The permeability of poly-L -methionine (PLM) membrane and its oxidized form to water vapor was studied. Permeability coefficients of the PLM membrane were large, of the order of 10^?7 cm³ (S.T.P.)·cm/cm²·sec·cm Hg. The sorption and permeation behavior of the PLM membrane was hydrophobic. The oxidized membrane was prepared by treating one or both sides of the PLM membrane with an aqueous solution of hydrogen peroxide. The membrane oxidized from one side is probably not layered but has a gradient of composition from one surface to the other. The amounts of water sorbed by the modified membrane increased with increase in oxidation time. The permeability coefficients of water vapor through the modified membrane were of the order of 10^?6 cm³ (S.T.P.)·cm/cm²·sec·cm Hg.     

Characterization of electrode/electrolyte interface for lithium batteries using in situ synchrotron X-ray reflectometry—A new experimental technique for LiCoO2 model electrode

A new experimental technique was developed for detecting structure changes at electrode/electrolyte interface of lithium cell using X-ray reflectometry and two-dimensional model electrodes with a restricted lattice-plane. The electrodes were constructed with an epitaxial film of LiCoO₂ synthesized by pulsed laser deposition method. The orientation of the epitaxial film depends on the substrate plane; the 2D layer of LiCoO₂ is parallel to the SrTiO₃ (1 1 1) substrate (_(0 0 3)LiCoO₂//_(1 1 1)SrTiO₃)$({(003)}_{\text{LiCo}{\text{O}}_2}//{(111)}_{\text{SrTi}{\text{O}}_3})$, while the 2D layer is perpendicular to the SrTiO₃ (1 1 0) substrate (_(1 1 0)LiCoO₂//_(1 1 0)SrTiO₃)$({(110)}_{\text{LiCo}{\text{O}}_2}//{(110)}_{\text{SrTi}{\text{O}}_3})$. The anisotropic properties were confirmed by electrochemical measurements. Ex situ X-ray reflectivity measurements indicated that the impurity layer existed on the as-grown LiCoO₂ was dissolved and a new SEI layer with lower density was formed after soaking into the electrolyte. In situ X-ray reflectivity measurements indicated that the surface roughness of the intercalation (1 1 0) plane increased with applying voltages, while no significant changes in surface morphology were observed for the intercalation non-active (0 0 3) plane during the pristine stage of the charge–discharge process.     

Directional permeability of asymmetrically oxidized poly(L-methionine) film to oxygen dissolved in water

The permeability of an asymmetrically oxidized poly(L-methionine) film to oxygen dissolved in water was examined. It was recognized that the permeability along an increasing gradient of oxidized methionine composition is higher than the gradient is reversed. A qualitative analysis of this result was presented in terms of the oxygen solubilities into the film and water absorbed in the film.