Metal oxide semiconductor-based hydrogen sensors: material engineering strategies for performance enhancement

Abstract

Hydrogen is recognized as a clean energy carrier whose safe and efficient utilization relies on accurate and reliable sensing technologies. Among various sensing mechanisms, resistive hydrogen sensors based on metal oxide semiconductors (MOS) have drawn considerable interest owing to their high sensitivity, fast response, low cost, and compatibility with integration. This review systematically outlines recent advances in MOS-based hydrogen sensors, focusing on representative materials such as SnO₂, ZnO, WO₃, and TiO₂. Starting from the intrinsic properties of these materials, including crystal structure, electronic band features, and defect chemistry, the underlying gas-sensing mechanisms are thoroughly analyzed. To enhance sensitivity, selectivity, response speed, and stability, four major material design strategies are examined in detail: nanostructure engineering, noble-metal functionalization, heterojunction construction, and defect control. These approaches act synergistically to tailor surface redox kinetics, catalytic activity, and interfacial charge transport, thereby enabling performance-oriented optimization of the sensors. Unlike a simple summary of reported materials and sensing performances, this review links intrinsic material properties, hydrogen-sensing mechanisms, and performance-enhancement strategies within a materials-oriented framework. By adopting a materials-centric and mechanism-oriented perspective, it aims to provide useful guidance for the rational design of high-performance MOS hydrogen sensors and to stimulate further progress in next-generation hydrogen detection technologies.