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Model EC4-100-H2S -Hydrogen Sulfide Electrochemical Sensor
SGX electrochemical sensors detect gases by producing a chemical reaction between the gas and oxygen contained in the sensor. This reaction produces a small current, which is proportional to the concentration of the gas present. The sensor is, in effect, a type of fuel cell.
Reactions occur on two electrodes which when combined together produce the sensing process. These electrodes comprise small discs of porous PTFE onto which is deposited a thin layer of a catalytic metal.
On the working electrode the target gas (carbon monoxide or hydrogen sulfide) react with water to produce either carbon dioxide or sulfuric acid, hydrogen Ions and 2 electrons On the counter electrode, oxygen reacts with hydrogen ions and electrons to form water, e.g.
- Working Electrode: CO + H2O ->■ CO2+ 2H+ +2e"
- Counter Electrode: 1/202 + 2H+ + 2e" -* H20
- Overall: CO + 1/202 -»C02
Because the electrodes have a finite catalytic activity (which can change with time and temperature) it is necessary to limit the rate of diffusion of target gas into the sensor (using a barrier) to ensure the gas is efficiently reacted.