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

Hydrogen gas (H 2 ) 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 H 2 production, storage and transportation are greatly limited. Hence, H 2 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 H 2 detection because of its easy synthesis, chemical/thermal stability and extremely abundant nanostructures. The recent advances in resistive-type H 2 gas sensors based on ZnO nanostructures are reviewed in this paper. According to zero-dimension, one-dimension, and two-dimension, the H 2 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 H 2 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 H 2 sensors to H 2 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 H 2 sensors are addressed as well.