Molecular Sieve Based on PMMA/ZIF-8 Bilayer for CO-Tolerable H 2 Sensor with Superior Sensing Performance

Semiconductor sensors equipped with Pd catalysts are promising candidates as low-powered and miniaturized surveillance devices that are used to detect flammable hydrogen (H ) gas. However, the following issues remain unresolved: (i) a sluggish sensing speed at room temperature and (ii) a deterioration of sensing performance caused by interfering gases, particularly carbon monoxide (CO). Herein, a bilayer comprising poly(methyl methacrylate) (PMMA) and zeolitic imidazolate framework-8 (ZIF-8) is utilized as a molecular sieve for diode-type H sensors based on Pd-decorated indium-gallium-zinc oxide film on a p-type silicon substrate. While the PMMA effectively blocks the penetration of CO gas molecules into the sensing entity, the ZIF-8 improves sensing performances by modifying the catalytic activity of Pd, which is preferable for splitting H and O molecules. Consequently, the bilayer-covered sensor achieves outstanding CO tolerance with superior sensing figures of merit (response/recovery times < 10 s and sensing response > 5,000% at 1% H ).