Fabrication of ZnO/Pd@ZIF-8/Pt hybrid for selective methane detection in the presence of ethanol and NO2

Abstract

The exploration of novel sensing materials for selective identification of methane (CH4) is critical for practical applications, particularly in the presence of ethanol (C2H5OH) and nitrogen dioxide (NO2), which are general interfering gases for the monitoring of CH4 in industrial and domestic scenarios. This work proposed a novel core-shell ZnO/Pd@ZIF-8/Pt nanomaterial to achieve CH4 selective sensing. At 230 °C, the CH4 selectivity against C2H5OH and NO2 of the ZnO/Pd@ZIF-8/Pt sensor is improved by 13.2 times and 76.5 times, respectively. Catalytic experiments revealed that Pt has a high selective catalytic activity to C2H5OH than CH4, indicating its catalytic filtering effect. Besides, the sieving effect of ZIF-8 can further hinder the interfering gas owing to its aperture size of 4.0–4.2 Å, where NO2 (4.5 Å) was retarded while CH4 (3.8 Å) can pass. Thus, these two effects synergistically contribute to the improved CH4 selectivity. The ZnO/Pd@ZIF-8/Pt also showed a response of 304.6% to 5000 ppm CH4 at 230 °C with a response/recovery time of 4.0 s / 1.5 s, as well as full reversibility and long-term stability, which is potential in practical CH4 detection. Furthermore, the combination of the gas-selective catalytic activity of noble metals with the MOF filter can be easily extended to other types of SMOs@MOF sensors, opening a new avenue for the preparation of highly selective sensor devices.