Accession Number : ADA294338

Title :   Natural Convection at Microelectrodes.

Descriptive Note : Technical rept.,

Corporate Author : UTAH UNIV SALT LAKE CITY DEPT OF CHEMISTRY

Personal Author(s) : Gao, Xiaoping ; Lee, Jeonghee ; White, Henry S.

PDF Url : ADA294338

Report Date : 31 MAR 1995

Pagination or Media Count : 21

Abstract : Steady-state voltammetric currents for Fe(CN)6(-4) oxidation and Fe(CN)6(-3) reduction in 0.2 M KCl solutions are shown to be a function of the orientation of Au and Pt rnicrodisk electrodes (radius = 6.4 to 25 micrometers) with respect to the gravitational field. The observed angular dependencies for the Fe(CN)6(-3/-4) couple are in agreement with theoretical expectations based on electrochemically-generated fluid density gradients within the depletion layer. The results demonstrate that steady-state voltammetric currents measured at microelectrodes are comprised of both diffusional and natural convection mass-transfer fluxes. At 25 micrometers-radius microdisks, natural convection accounts for between 2 and 13% of the total current for redox concentrations between 10 and 500 mM, respectively. The contribution of mass-transfer due to natural convection is shown to rapidly decrease with decreasing electrode size. jg

Descriptors :   *CONVECTION, DEPLETION, STEADY STATE, DENSITY, SIZES(DIMENSIONS), LAYERS, ELECTROCHEMISTRY, IRON COMPOUNDS, ELECTRODES, PLATINUM, FLUIDS, CYANIDES, DIFFUSION, POTASSIUM CHLORIDE, GOLD, VOLTAMMETRY, CURRENTS, OXIDATION REDUCTION REACTIONS, GRADIENTS, GRAVITATIONAL FIELDS.

Subject Categories : Physical Chemistry
      Inorganic Chemistry
      Electricity and Magnetism
      Fluid Mechanics

Distribution Statement : APPROVED FOR PUBLIC RELEASE