Low-cost ZnO nanorod-based hydrogen gas sensor with dipole-induced H2 sensing mechanism

Hydrogen (H 2 ) is a highly flammable and colorless gas, necessitating the development of reliable, low-cost sensors for its safe detection in industrial and environmental settings. In this work, one-dimensional (1D) zinc oxide (ZnO) nanorods were synthesized on glass substrates using a cost-effective aqueous hydrothermal method and investigated for H 2 gas sensing applications. Structural and morphological analyses confirmed the formation of vertically aligned ZnO nanorods with a hexagonal wurtzite structure, high crystallinity, and uniform c-axis growth. Electrical characterization exhibited linear current–voltage (I–V) behavior, consistent with Ohmic conduction. Upon exposure to 2000 ppm of H 2 gas, the sensor's resistance decreased from 0.623 MΩ to 0.563 MΩ, indicating a clear and repeatable sensing response. However, only a partial recovery to 0.566 MΩ was observed after 5 minutes in air, suggesting moderate recovery behavior under the tested conditions. The sensing mechanism is attributed to dipole-induced dipole interactions between the anisotropic ZnO surface and non-polar H 2 molecules. These findings demonstrate that ZnO nanorods offer strong potential as low-cost, sensitive hydrogen gas sensors, though further optimization is needed to improve response dynamics and recovery performance for practical deployment.