Sensor adopt solid electrolyte cell Princip le,It is composed by the following solid cells:
Air,Au|NASICON|| carbonate|Au, air,CO2
When the sensor exposed to CO2,the following electrodes reaction occurs:
Cathodic reaction:2Li + + CO2 + 1/2O2 + 2e - = Li2CO3
Anodic reaction:2Na+ + 1/2O2 + 2e- = Na2O
Overall chemical reaction:Li2CO3 + 2Na + = Na2O + 2Li + + CO2
The Electromotive force(EMF) result from the above electrode reaction, accord with according to Nernst’s equation::
EMF = Ec - (R x T) / (2F) ln (P(CO2))
P(CO2)—CO2--- partial Pressure Ec—Constant Volume R—Gas Constant volume
T— Absolute Temperature (K)F—Faraday constant
From Figure 1B, Sensor Heating voltage supplied from other circuit , When its surface temperature is high enough ,
the sensor equals to a cell, its two sides would output voltage signal ,and its result accord with Nernst’s equation。 In
sensor testing, the impedance of amplifier should be within 100—1000GΩ,Its testing current should be control below
1pA.