Electrochemical cell method

Method 5 Electrochemical cell method : galvanic cell type

Features

  • A simple detector mechanism that is compact and lightweight and can be used for portable analyzers.
  • Can be used even if flammable or corrosive gases coexist in the sample gas.
  • No carrier gas required.
Structure and operating principle of electrochemical cell method galvanic cell type of oxygen analyzer

Figure 5: Structure and operating principle of electrochemical cell method galvanic cell type of oxygen analyzer

Measuring principle, structure and operating principle (Figure 5)

When a metal that is soluble in an electrolyte (base metal as the positive electrode of the cell) and a metal that is insoluble (precious metal as the negative electrode of the cell) are immersed in the electrolyte, the metal dissolves at the positive electrode and releases electrons, which reach the negative electrode. At the negative electrode, the oxygen permeated through the thin film takes in electrons. (galvanic cell)

Reaction at positive electrode and negative electrode 

Positive electrode
2Pb + 4OH- → 2PbO + 2H2O + 4e-
Negative electode
O2 + 2H2O + 4e- → 4OH-

Since the current by  this electron flow is proportional to the oxygen permeated through the thin film, the oxygen concentration can be obtained by measuring this current.

Figure 5 shows a typical galvanic cell type oxygen analyzer that uses potassium hydroxide (KOH) as the electrolyte, lead(Pb) as the positive electrode, silver(Ag) as the negative electode, and fluorine-resin film as the thin film that permeats oxygen.


Related products

The galvanic cell type analyzer can be used continuous oxygen measurement in various processes, even when flammable or corrosive gases coexist in the sample gas. In addition to gas measurement, it is used for continuous measurement of dissolved oxygen in water and liquids.

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