Electric response to polluting gases

For several couples of sensitive electrodes to oxygen action, it seemed interesting to test them in the presence of other gases like carbon monoxide or nitrogen oxides. Rhodium is indeed considered a good catalyst for the reduction of nitrogen oxides. Thus, we wanted to compare the observed sensitivities in order to determine selectivity criteria, and subsequently to be able to detect these different gases. 

For this purpose, we have tested the platinum/gold, platinum/rhodium and rhodium/gold couples. 

The injection of 300 ppm of carbon monoxide in the air imphes a positive response for all the sensors, a result characteristic of a reducing gas. 

The greatest response is given for the Pt/Au couple. This corrfirms that these two metals have a great difference in their catalytic activities as far as the oxidation of carbon monoxide is concerned. 

The response of the Pt/Au and Rh/Au sensors in the presence of the mixture CO + NO2 indicates a decrease in the signal, confirming the presence of oxidizing gas NO2. 

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