Report on the source of the electrochemical impedance on cermet inert anodes

Technical Report · Fri Feb 01 04:00:00 EST 1991

DOI:https://doi.org/10.2172/6104660· OSTI ID:6104660

Windisch, Jr, C F; Stice, N D

the Inert Electrode Program at Pacific Northwest Laboratory (PNL) is supported by the Office of Industrial Processes of the US Department of Energy and is aimed at improving the energy efficiency of Hall-Heroult cells through the development of inert anodes. The inert anodes currently under study are composed of a cermet material of the general composition NiO-NiFe{sub 2}O{sub 4}-Cu. The program has three primary objectives: (a) to evaluate the anode material in a scaled-up, pilot cell facility, (b) to investigate the mechanisms of the electrochemical reactions at the anode surface, and (c) to develop sensors for monitoring anode and/or electrolyte conditions. This report covers the results of a portion of the studies on anode reaction mechanisms. The electrochemical impedances of cermet inert anodes in alumina-saturated molten cryolite as a function of frequency, current density, and time indicated that a significant component of the impedance is due to the gas bubbles produced at the anode during electrolysis. The data also showed a connection between surface structure and impedance that appears to be related to the effects of surface structure on bubble flow. Given the results of this work, it is doubtful that a resistive film contributes significantly to the electrochemical impedances on inert anodes. Properties previously assigned to such a film are more likely due to the bubbles and those factors that affect the properties and dynamics of the bubbles at the anode surface. 12 refs., 16 figs., 3 tabs.

• Research Organization: Pacific Northwest Lab., Richland, WA (USA)
• Sponsoring Organization: DOE; USDOE, Washington, DC (USA)
• DOE Contract Number: AC06-76RL01830
• OSTI ID: 6104660
• Report Number(s): PNL-7629; ON: DE91008427
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360204 -- Ceramics
Cermets
& Refractories-- Physical Properties
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400400* -- Electrochemistry
ALUMINIUM
ALUMINIUM COMPOUNDS
ALUMINIUM OXIDES
ANODES
BUBBLES
CERMETS
CHALCOGENIDES
CHEMICAL REACTIONS
COMPOSITE MATERIALS
CORROSION
CURRENT DENSITY
DATA
ELECTRIC IMPEDANCE
ELECTRICAL PROPERTIES
ELECTROCHEMICAL CELLS
ELECTRODES
ELECTROLYSIS
ELEMENTS
EXPERIMENTAL DATA
IMPEDANCE
INFORMATION
LYSIS
MATERIALS
METALS
NUMERICAL DATA
OXIDES
OXYGEN COMPOUNDS
PHYSICAL PROPERTIES
PLATINUM
PLATINUM METALS
SURFACE PROPERTIES
TRANSITION ELEMENTS