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High-performance catalysts are crucial for many applications, including high-performance gas sensors. However, the catalysts used in gas sensors need to be screened through many experimental measurements, which is time-consuming and labor-intensive. Herein, the catalytic activity of ZSM-5 zeolites with different Si/Al ratios is quantitatively evaluated using a resonant microcantilever that enables in-situ temperature-programmed desorption (cantilever-TPD) measurements. Since the frequency shift obtained by the cantilever-TPD measurement is proportional to the number of probe molecules, the cantilever-TPD experiment can successfully measure the number of active sites and desorption activation energy of the catalyst. Therefore, the cantilever-TPD experiment quantitatively characterizes the catalytic activity through the comprehensive analysis of the number of active sites and the desorption activation energy, eliminating the need for the traditional trial-and-error method to study the gas-sensing performance. According to the test results of cantilever-TPD, the ZSM-5 zeolite with satisfactory performance is preferred as the catalytic material, and the ZnO/ZSM-5 double-layer sensor is made to detect trace amounts of the greenhouse gas Freon R134a. The gas sensing results show that the optimized ZSM-5 sensor has good sensitivity, limit of detection (LOD), repeatability, and selectivity, fully confirming the evaluation results of the cantilever-TPD. • Resonant microcantilever is used for TPD measurements of catalytic-induced sensing materials. • The catalytic activity of ZSM-5 zeolites with different Si/Al ratios has been quantitatively evaluated. • ZSM-5 zeolite, with satisfactory performance, was selected as the catalytic-induced sensing material. [ABSTRACT FROM AUTHOR]

Freon R134a is a widely used refrigerant that can cause a severe greenhouse effect and should be detected on site. However, it is a big challenge for semiconductor gas sensors to detect the inert Freon R134a molecules. Herein, mesoporous γ-Al 2 O 3 is synthesized and loaded on top of ZnO sensing materials to form a bilayer microsensor to realize high-performance detection of Freon R134a. The mesoporous γ-Al 2 O 3 material first decomposes the inert R134a molecule into a large number of active radicals. The generated reactive radicals are then easily sensed by the ZnO material. The limit of detection (LOD) of the bilayer sensor reaches the ppm level, which meets the requirements for on-site detection of Freon R134a leakage. The online mass spectrum (online MS) is used to identify the produced radicals qualitatively. According to the online MS results, the catalytic mechanism of mesoporous γ-Al 2 O 3 for Freon R134a molecules has been clearly revealed. • Mesoporous γ-Al 2 O 3 is synthesized for the detection of Freon R134a. • Micro-hotplates are manufactured using MEMS technology. • The MEMS microsensor shows mW-level power consumption. • Mesoporous γ-Al 2 O 3 has good catalytic activity for Freon molecules. • Mass spectrometry (MS) techniques are used to reveal the sensing mechanism. [ABSTRACT FROM AUTHOR]