A selective methane gas sensor with printed catalytic films as active filters

In this work, a selective methane gas sensor was prepared based on In 2 O 3 to eliminate the serious cross-sensitive sensitivity to VOCs, NO 2 , and CO, which are typical interfering gases for methane detection in domestic. The catalytic films of Pt-TiO 2 , Pt-CeO 2 , and Pt-ZrO 2 were placed on the top of the sensing layer, i.e., In 2 O 3 loaded with Pd. Catalytic films were designed as filters to catalytically oxidize the interfering gases, such as VOCs, to prevent them reaching the surface of the sensitive layers. Thanks to this design, our sensors showed a high selectivity to methane, even in the presence of ethanol, CO, and NO 2 . In addition, we confirmed via the power-law response of oxygen that the basic sensing mechanism between Pd-In 2 O 3 and the sensor-printed catalytic films are kept the same. Both follow the general model with MOS sensors, which involves an electron transfer process resulting from the adsorption of oxygen on the surface and interaction with methane molecules. The present study showed that catalytic filter films (Pt-TiO 2 , Pt-CeO 2 , and Pt-ZrO 2 ) printed on Pd-In 2 O 3 sensors could enhance the selective response to methane for methane monitoring.