1997 Fiscal Year Final Research Report Summary
Extension of the Service Life of IrO_2 Anodes by the Addition of Colloidal Silica
| Project/Area Number |
08455329
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Material processing/treatments
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| Research Institution | The University of Tokyo |
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Principal Investigator |
MUSHIAKE Katsuhiko The University of Tokyo, Institute of Industrial Science, Research Assistant, 生産技術研究所, 助手 (10092347)
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| Co-Investigator(Kenkyū-buntansha) |
MITSUDA Yoshitaka The University of Tokyo, Institute of Industrial Science, Associate Professor, 生産技術研究所, 助教授 (20212235)
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| Project Period (FY) |
1996 – 1997
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| Keywords | IrO_2 electrode / Colloidal silica / Gradient concentration / Electrocatalyst / Extended service life |
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| Research Abstract |
Iridium oxide electrodes have become increasingly important as industrial metal anodes for oxygen evolution reaction owing to the significant advances in electrolytic processes. Cast lead alloys have been commonly used as insoluble anodes but have some drawbacks such as a high overpotential for the oxygen evolution reaction, lead contamination of products and short circuiting by deformations. These difficulties can be however overcome by the use of iridium oxide electrodes. One shortcoming of the metal electrodes is undesirable catalyst loss due to attack by organic substances dissolved in baths.
To promote the stability of the metal electrodes, silica particles of colloidal size were dispersed in the electrocatalysts and it was shown that the service life of the electrodes was increased with the square power of the total number of coating. It has thus become possible to prepare the durable electrodes with reduced number of coating. The peculiar relation describing the effect of colloidal silica on the service life prompted the depth profiling study of the layred catalysts. Experimental observation with an electron probe microanalyzer and scanning electron microscope has shown that the catalyst films consisted of triplex layrs with an IrO_2-enriched outside, an SiO_2-enriched inside, and an intermediate section where the two oxides interpenerated. Colloidal silica supplied at the surface of films thus easily through the layrs inward to form further SiO_2-enriched layrs. In order words, silica gradient concentrations are built into films ; such gradient concentrations result in the reduction in the loss rate and appear to give anode films their long service life.
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