The Development of Metal Doped Zinc Oxide Nanostructures for Hydrogen Sensors: A Review

Abstract

Zinc oxide (ZnO) nanostructures have garnered significant attention as potential materials forhydrogen (H2) sensing applications due to their unique properties, such as high surface area, tuneablemorphology, and excellent electrical conductivity. The introduction of metal doping into ZnO nanostructures has been shown to enhance their performance by improving sensitivity, selectivity, and response time to H2gas. This review provides a comprehensive overview of the advancements in the development of metal-doped ZnO nanostructures for H2sensing. Key metal dopants, including transition metals, alkali metals, and rare-earth metals, are discussed in terms of their effects on the structural, electronic,and optical properties of ZnO, which ultimately influence their H2-sensing capabilities. The review also examines various techniques employed to fabricate metal-doped ZnOnanostructures, such as sol-gel, hydrothermal, and chemical vapour deposition methods, highlighting their advantages and limitations. Additionally, the mechanisms underlying H2sensing in metal-doped ZnO nanostructures, including adsorption, charge transfer, and catalytic effects, are explored. Furthermore, the challenges related to stability, repeatability, and selectivity in real-world applications are addressed. Finally, future research directions and potential strategies for overcoming these challenges, including the exploration of hybrid nanomaterials, composite structures, and the optimisation of doping concentrations, are discussed. This review aims to provide valuable insights for researchers and engineers in the development of advanced H2sensors based on metal-doped ZnO nanostructures, contributing to the improvement of safety, energy efficiency, and environmental monitoring.