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.