Study on simultaneous detection of CO and H₂ with (Pd, Fe)-modified SnO₂ and Pt-loaded SnO₂ sensors

The (Pd, Fe)-modified SnO₂ (S1) and Pt-loaded SnO₂ (S2) are synthesized via a sol–gel method. As S1 has better selectivity to CO against H₂ while S2 to H₂ against CO at 400 °C. Thus S1 and S2 can be used to detect the concentration of CO and H₂, respectively. However, neither S1 nor S2 can detect the concentration of CO and H₂ when they coexist. In this paper, S1 and S2 sensors are used simultaneously for mixed gas of CO and H₂ detection, and the respective concentration of CO and H₂ is calculated. The calculation process is explained as follows: the response of S1 (R₁) and S2 (R₂) to a fixed concentration of mixed gas of CO and H₂ is obtained in experiment, respectively. So we can calculate the concentration of CO and H₂ by using simultaneous equations with the independent variable R₁ and R₂. Contrast real values with calculated values of CO and H₂ concentration, the error margin are all less than 5%, which indicates that this method may be a promising candidate for enhancing the selectivity of semiconductor-based gas sensor to two or more gases.