An efficient hydrogen gas sensor based on hierarchical Ag/ZnO hollow microstructures

Abstract The design of hierarchical zinc oxide (ZnO) microstructures modified with silver (Ag) nanoparticles have emerged as an effective approach for improving the hydrogen gas sensing performance. Here, we report a simple, low-cost chemical co-precipitation method to obtain the Ag/ZnO hollow microstructures and morphologically characterized them by field emission scanning electron microscopy (FESEM). FESEM images revealed the clear hollow hexagonal tube-like morphology. The existence of Ag in ZnO was confirmed by X-ray diffraction (XRD) and energy-dispersive X-ray spectroscopy (EDS). UV visible absorption and photoluminescence (PL) spectra were also recorded to observe the effect of Ag nanofiller on the optical properties of ZnO. Furthermore, the gas sensing properties of the as-prepared bare ZnO and Ag/ZnO sensor were investigated. The thoroughly sensing experiments demonstrated that after modification with Ag nanoparticles the ZnO sensor shows superior sensitivity 479 % towards 300 ppm hydrogen gas concentration, whereas 101 % response was noted for the pure ZnO sensor at 250 °C working temperature. Meanwhile, Ag/ZnO hybrids exhibited excellent selectivity, fast response, and recovery time and also obtained a good and stable response signal at 5 ppm H2 exposure, which indicated that the lower concentration measurement is also attainable. This enhancement in the sensing performance of Ag/ZnO structures towards hydrogen is due to the chemical and electronic sensitization effect of Ag nanoparticles. As a result, such microstructure is attributed to more oxygen species and active sites, and it enhances the sensitivity of a sensor. Moreover, this type of hybrid opens a new path and supports the next generation of innovative materials to fabricate highly selective and sensitive H2 gas sensing devices.