pH sensor properties of electrochemically grown iridium oxide


Olthuis, W. and Robben, M.A.M. and Bergveld, P. and Bos, M. and Linden, W.E. van der (1990) pH sensor properties of electrochemically grown iridium oxide. Sensors and Actuators B: Chemical, 2 (4). pp. 247-256. ISSN 0925-4005

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Abstract:The open-circuit potential of an electrochemically grown iridium oxide film is measured and shows a pH sensitivity between −60 and −80 mV/pH. This sensitivity is found to depend on the state of oxidation of the iridium oxide film; for a higher state of oxidation (or more of the oxide in the high valence state), the sensitivity is also higher. This high sensitivity can be explained on the basis of the extra proton release as a result of the acidic character of the porous hydrous oxyhydroxide, in combination with the redox behaviour.

The response time to a pH step is measured and is found to depend mainly on the thickness of the oxide; it varies from 40 ms to 0.35 s due to the porous nature of the film.

Drift measurements show that an iridium oxide film in reduced state is slowly oxidized by dissolved oxygen, whereas a pre-oxidized film in a pH = 4.01 buffer solution in contact with air shows a long-term drift of <0.3 mV/h.
Item Type:Article
Copyright:© 1990 Elsevier
Electrical Engineering, Mathematics and Computer Science (EEMCS)
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