An unusually high sensitivity of Pt-black pH electrode

Abstract

The potentials of Pt-black electrode using a copper conducting wire instead of the salt bridge in acid and alkaline solutions without the use of H2 evolution reactions were measured. There were three nonlinear portions in the calibration curve. Unusually, the potential slopes at pH 3–5 and 8–10 indicated 200 mV and 70 mV per pH, respectively. Such high sensitivity for pH slope, more than 4 times of usual 59 mV per pH, may be credited to the special properties of the Pt-black surface. SEM (scanning electronical microscopy) was applied to characterize the surface of the Pt-black electrode. Its working mechanism is well explained in the theory of capacitance potentials rather than Nernst’s redox potentials.

Keywords

Pt-black pH electrode / sensitivity / capacitance potential

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