Carbon-based materials coupled with metal oxide semiconductors for hydrogen sensors: linking mechanisms and dimensions

Abstract

Reliable H 2 detection is essential for hydrogen energy systems, industrial processing, battery safety, and clinical monitoring. Chemiresistive sensors based on metal oxide semiconductor (MOS) are widely used because of their low fabrication cost and facile integration. However, they still suffer from high operating temperatures, limited selectivity, poor humidity tolerance, and insufficient long-term stability. Incorporating carbonaceous materials with large specific surface areas, high carrier mobility, and tunable surface chemistry provides an effective route to address these limitations. This review summarizes recent advances in the carbon-enabled optimization of MOS hydrogen sensors, with emphasis on electronic sensitization, heterojunction modulation, interfacial charge transfer, gas-diffusion regulation, defect engineering, surface hydrophobicity, and resistance to degradation. Composite systems are classified into zero-, one-, two-, and three-dimensional carbon architectures, and their geometry-dependent advantages and engineering limitations are compared. Subsequently, we discuss several performance metrics relevant to industrial applications, including room-temperature sensing, selectivity, humidity resistance, low-frequency noise, flexible and wearable integration, novel porous materials, and unified testing protocols. Finally, we assess machine-learning-assisted sensor-array analysis for gas discrimination and drift compensation and outline the data requirements for AI-assisted material screening. Through comparative analysis, we conclude that no single carbon material is universally optimal for all sensing processes and operating conditions. Material selection with respect to dimensionality, surface chemistry, loading level, and interfacial configuration should be guided by specific application requirements. Moreover, AI-assisted sensing, and complementary sensor arrays is a promising strategy for reliable hydrogen detection in complex environments.