Enhanced long-term stability of SnO2-based CO gas sensors modified by sulfuric acid treatment

The gas-sensing properties and long-term transients of SnO2-based CO gas sensors modified by sulfuric acid treatments have been investigated. The sulfuric acid treatments are carried out in two ways: kneading of SnO2 powders with a sulfuric acid solution or dipping of the sintered sensor element in the same solution. Both sulfuric acid treatments enhance the sensitivity to CO and H2, although the enhancement is more remarkable with the dipping treatment. The effects of these treatments on the selectivity to CO and some parameters relating to the reversibility and accuracy for CO detection are also evaluated. Furthermore, the long-term stabilities of the modified and unmodified sensor elements for over 550 days are investigated. The results indicate that the dipping treatment significantly improved the stability and reliability of the SnO2-based CO gas sensor.