Exploring novel sensing materials to rapidly identify CH4 at low temperatures is crucial for various practical applications. Herein, a novel ZnO-xBa/Pd with Ba of cocatalyst loading from 0 to 2.0 wt% was facilely prepared using a two-step impregnation method to improve the sensitivity of the CH4 gas sensor. The microstructure, chemical states of the elements, and surface properties of ZnO-Ba/Pd were characterized, and the gas-sensitive performance of ZnO-Ba/Pd sensors was investigated. Compared to methane sensors based on other inorganic and organic material sensors, the sensor based on ZnO-1.0Ba/Pd exhibited a faster response/recovery time (1.4 s/8.3 s) and higher response (368.2%) for 5000 ppm CH4 at a lower temperature (170 °C). Moreover, the ZnO-1.0Ba/Pd sensor exhibited full reversibility and long-term stability, as well as excellent selectivity at 170 °C. The excellent performance of the ZnO-Ba/Pd sensor was attributed to the electron donation by Ba, which increases the electron density around Pd, thus enhancing the catalytic activity of Pd and promoting oxygen adsorption on the ZnO surface. The present work provides a method for the rational design and synthesis of sensitive materials in practical CH4 detection.
Highly sensitive and selective methane (CH4) gas detection is a critical challenge in complex practical scenarios. Herein, this work presents an excellent CH4 gas sensor based on ZnO/Pd nanorods encapsulated in a zeolitic imidazolate framework (ZIF)-7 shell. Compared with the ZnO/Pd sensor, the ZnO/Pd@ZIF-7 sensor exhibited a faster response/recovery time (2.3/8.3 s) and higher response (668.5%) toward 5000 ppm of CH4 gas at 180 °C. Furthermore, a 22-fold higher selectivity to CH4 against ethanol (C2H5OH) was observed. The improved sensitivity and selectivity of the ZnO/Pd@ZIF-7 sensor are attributed to the dual roles played by the ZIF-7 shell; first, it generates more chemisorbed oxygen on the ZnO surface while improving the catalytic activity of Pd, and it facilitates the catalytic oxidation of CH4 and ultimately improves the sensitivity. Moreover, the ZIF-7 shell has filtering effects, which significantly reduces the response of interfering gases and exhibits excellent CH4 selectivity. This paper explores the strategy of combining a dual-functional ZIF-7 shell with ZnO/Pd, proposing a gas sensor design concept that broadens the application of metal–organic framework materials for CH4 detection.
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