Accession Number : ADA119144

Title :   Thermodynamics and Photoelectrochemical Behavior of the n-TiO2 Electrode in Fluoride Containing Solutions.

Descriptive Note : Technical rept.,


Personal Author(s) : Hepel,Tadeusz ; Hepel,Maria ; Osteryoung,R. A.

Report Date : 01 SEP 1982

Pagination or Media Count : 54

Abstract : Diagrams of the stable and metastable electrochemical equilibria for the system Ti - HF - H20 at 25 C have been constructed. Increased solubility of titanium dioxide in fluoride containing solutions has been found to occur over a narrow range of solution pH near 3.2. On the basis of the thermodynamic diagrams, appropriate conditions for etching n-Ti02 semiconductor electrodes were chosen. The etching solutions prepared for the n-Ti02 semiconductor electrodes showed very good surface-cleansing properties. A photoetching process under anodic bias is recommended for the preparation of the n-Ti02 surface for the purpose of use in solar energy converters. The doping profile in the space-charge layer which forms during the photoetching treatment is more effective for splitting the electron-hole pair created in a working electrochemical solar cell. Photocurrent-voltage characteristics obtained for n-Ti02 electrodes in F- solutions do not fit the Butler-Gartner equation, since the Butler-Gartner equation does not correctly describe photoeffects on medium and heavily doped semiconductor electrodes. From the chronovoltamperometric and coulometric study of the reactions taking place at electrode potentials negative of the flat-band potential, only the first step of the Ti02 reduction to lower oxides is reversible. (Author)

Descriptors :   *Photochemical reactions, *Thermodynamics, *Electrodes, *Anodic coatings, *Electrochemistry, Titanium oxides, Fluorides, Electrons, Holes(Electron deficiencies), Solubility, Solar cells, Doping, Etching, Energy conversion, Layers

Subject Categories : Physical Chemistry
      Radiation and Nuclear Chemistry

Distribution Statement : APPROVED FOR PUBLIC RELEASE