In:
Israel Journal of Chemistry, Wiley, Vol. 18, No. 1-2 ( 1979-01), p. 125-130
Abstract:
Electropolished Ni(110) electrodes have a highly epitaxed 4 to 6 Å thick NiO surface film which is cathodically reduced in pH 2.8 Na 2 SO 4 solution with a current efficiency of ∼ 60%. This oxide breaks down rapidly on open circuit in the same solution giving an arrest structure which, in conjunction with surface activity measurements, indicates localized removal of a very defective film. The open‐circuit breakdown characteristics of anodically formed passive oxide films indicate that these films contain a localized distribution of defects within the oxide. The number of defects and their stability is found to be highly dependent upon the condition of anodization. With increasing time of anodization at potentials in the passive region, the number of defect sites decreases and/or their stability increases, i.e. the film becomes more perfect The corresponding decrease in anodic current with increasing time of anodization indicates a correlation between this current and the electrochemical reactions at the defect sites. The anodic current is due mainly to nickel dissolution which occurs after breakdown and during inefficient repair of the defect oxide. Analysis of the passive oxide film indicates the presence of 9 to 12 Å of NiO. The time and potential of anodization has little effect on the average thickness or stoichiometry of the passive film, the condition of anodization only influencing the small (≦2%) coverage of defect sites on the surface. The passive film can be cathodically reduced but with only a very low current efficiency. The results obtained with the Ni(110) surface are in general agreement with those previously obtained for Ni(111) and Ni(100) electrodes.
Type of Medium:
Online Resource
ISSN:
0021-2148
,
1869-5868
DOI:
10.1002/ijch.v18:1-2
DOI:
10.1002/ijch.197900015
Language:
English
Publisher:
Wiley
Publication Date:
1979
detail.hit.zdb_id:
2066481-3
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