Thermal decomposition-assisted, aspect ratio controlled ZnO nanorods towards highly selective H₂ gas detection

ZnO nanostructures with various aspect ratios have been synthesized for H₂ gas detection applications. The thermal-decomposition method was employed at different annealing temperatures (350, 450, and 550 °C) and its impact on various shapes/sizes of ZnO nanostructures is demonstrated. Thermal decomposition performed at 350 °C exhibited a maximum (∼6.25) aspect ratio among them. Its capability of H₂ sensing was also observed to be maximum by realizing ∼483% of sensor response at 180 °C under H₂ gas concentration of 80 ppm. The sensor response is ∼3 times (∼177%) and ∼9 times (∼53%) higher at ZnO nanostructure synthesized at 350 °C than at 450 °C, and 550 °C, respectively. The higher sensor response has been attributed to the increased availability of active surface area for adsorption/desorption of gas molecules. ZnO@350 nanostructure showed significantly higher selectivity towards H₂ gas than other target chemical inputs. We have also studied H₂-induced metallization on the surface of ZnO nanostructures which plays an important role for improving the selectivity and sensor response. This study provides insight into the role of aspect-ratio-controlled shape/sized ZnO in improving H₂ gas sensing.