Selective detection of methane by Pd-In2O3 sensors with a catalyst filter film

Gas sensors based on In 2 O 3 were prepared and were found to be very sensitive to methane with Pd loading (Pd-In 2 O 3 ), even at a low temperature of 300 °C. However, Pd-In 2 O 3 sensors suffer from a high cross-sensitive response to NO 2 , CO and ethanol, which are typical interfering gases for the detection of CH 4 . In order to promote the selective response to CH 4 , a filter based on Pt-Al 2 O 3 catalyst film was printed onto the top of Pd-In 2 O 3 sensor layer. It was found that catalytic film coated sensors could selectively respond to methane even in the mixture of methane with CO, NO 2 , and ethanol. The cross-sensitive responses to the interference of VOCs, CO, NO 2 were almost eliminated. According to the catalytic conversion measurement, it was indicated that CO and ethanol were fully and selectively oxidized to CO 2 and H 2 O. In case of NO 2 , it was proposed that nitrogen dioxide molecules may be blocked on the surface of the catalyst film. Based on the oxygen adsorption behavior, it was suggested the printed catalyst film has no change on the basic sensing mechanism of In 2 O 3 based sensors following the general model that is the adsorption of oxygen and interaction with methane molecule and the resulted electron transfer process. Our investigation demonstrated that Pt-Al 2 O 3 printed Pd-In 2 O 3 sensor could be used for the detection of CH 4 leakage and monitor.