Structural transformation of nickel hydroxide films during anodic oxidation
The transformation of anodically formed nickel hydroxide/oxy-hydroxide electrodes has been investigated. A mechanism is proposed for the anodic oxidation reaction, in which the reaction interface between the reduced and oxidized phases of the electrode evolves in a nodular topography that leads to inefficient utilization of the active electrode material. In the proposed nodular transformation model for the anodic oxidation reaction, nickel hydroxide is oxidized to nickel oxy-hydroxide in the region near the metal substrate. Since the nickel oxy-hydroxide is considerably more conductive than the surrounding nickel hydroxide, as further oxidation occurs, nodular features grow rapidly to the film/electrolyte interface. Upon emerging at the electrolyte interface, the reaction boundary between the nickel hydroxide and oxy-hydroxide phases spreads laterally across the film/electrolyte interface, creating an overlayer of nickel oxy-hydroxide and trapping uncharged regions of nickel hydroxide within the film. The nickel oxy-hydroxide overlayer surface facilitates the oxygen evolution side reaction. Scanning tunneling microscopy of the electrode in its charged state revealed evidence of 80 {endash} 100 Angstrom nickel oxy-hydroxide nodules in the nickel hydroxide film. In situ spectroscopic ellipsometer measurements of films held at various constant potentials agree quantitatively with optical models appropriate to the nodular growth and subsequent overgrowth of the nickel oxy-hydroxide phase. A two-dimensional, numerical finite difference model was developed to simulate the current distribution along the phase boundary between the charged and uncharged material. The model was used to explore the effects of the physical parameters that govern the electrode behavior. The ratio of the conductivities of the nickel hydroxide and oxy-hydroxide phases was found to be the dominant parameter in the system.
- Research Organization:
- Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
- Sponsoring Organization:
- USDOE; USDOE, Washington, DC (United States)
- DOE Contract Number:
- AC03-76SF00098
- OSTI ID:
- 5058501
- Report Number(s):
- LBL-32136; ON: DE92016926
- Resource Relation:
- Other Information: Thesis (Ph.D.). Thesis. Submitted by R. W. Crocker
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
36 MATERIALS SCIENCE
NICKEL HYDROXIDES
ANODIZATION
OXIDATION
ELECTRODES
ELLIPSOMETRY
FILMS
FINITE DIFFERENCE METHOD
MATHEMATICAL MODELS
MICROSCOPY
MORPHOLOGY
CHEMICAL COATING
CHEMICAL REACTIONS
CORROSION PROTECTION
DEPOSITION
ELECTROCHEMICAL COATING
ELECTROLYSIS
HYDROGEN COMPOUNDS
HYDROXIDES
ITERATIVE METHODS
LYSIS
MEASURING METHODS
NICKEL COMPOUNDS
NUMERICAL SOLUTION
OXYGEN COMPOUNDS
SURFACE COATING
TRANSITION ELEMENT COMPOUNDS
250903* - Energy Storage- Batteries- Materials
Components
& Auxiliaries
360105 - Metals & Alloys- Corrosion & Erosion