Review-Resistive-Type Hydrogen Sensors Based on Zinc Oxide Nanostructures

Hydrogen gas (H2) is used as an alternative renewable and eco-friendly energy source to replace the fossil fuel. However due to its explosive risks in air, the H2 production, storage and transportation are greatly limited. Hence, H2 sensor with quick response, highly sensitive and selective detection is of importance. Recently, zinc oxide (ZnO) as n-type semiconductor has attracted much attention in the field of H2 detection because of its easy synthesis, chemical/thermal stability and extremely abundant nanostructures. The recent advances in resistive-type H2 gas sensors based on ZnO nanostructures are reviewed in this paper. According to zero-dimension, one-dimension, and two-dimension, the H2 sensing properties and related mechanism of various kinds of pristine ZnO nanostructures-based sensors, such as nanowires, nanotubes, and nanofibers are summarized and compared. Furthermore, this paper focuses on strategies to improve the performance of H2 sensors (sensitivity, response speed, operation temperature, and limit of detection) by the surface modification, metal doping, formation of composite, and post-treatment of ZnO nanomaterials. Especially, the selectivity of ZnO nanosturctures-based H2 sensors to H2 in the presence of interfering gases is highlighted and the related enhancement approaches are discussed. Finally, the outlook and challenges on the ZnO nanostructures-based H2 sensors are addressed as well.