PPM-Level Hybrid Hydrogen Sensor Based on Pd-Doped Amorphous WO3 QDs With Room-Temperature Gasochromic and Resistive Sensing

Gasochromic hydrogen sensors have significant potential for monitoring geometrically complex leakage points; however, they face challenges, including subtle and slow color changes, as well as high detection limits. To address these limitations, we developed a ppm-level hybrid hydrogen sensor with a gasochromic and resistive sensing capability. The sensing material comprises amorphous WO3 quantum dots (a-WO3 QDs) loaded with Pd nanoparticles, prepared using an anodization-photochemical reduction method. Owing to the small average size and large specific surface area of the a-WO3 QDs loaded Pd nanoparticles, the designed sensor was demonstrated to exhibit excellent sensitivity at low work temperature (room temperature, RT). The corresponding $\Delta {E}$ (color difference metric) curves were quantified via a smartphone-based colorimetric app. The hybrid sensor exhibited evident color changes ( $\Delta {E}=51$ ) in just 20 s for 1% hydrogen, with the lower limit of detection (LOD) being 200 ppm. The sensor can be characterized by its direct naked-eye detection capability, intrinsic safety (absence of an electrical system), lower detection limits, and operation capability at RT. Moreover, the diverse forms of gasochromic sensing, including powder, film, and gel, show promise for a wide range of applications, such as complex pipeline systems. The concurrent resistive-sensing capability of the hybrid sensor offers a lower LOD of 50 ppm, further complementing the overall performance. This work contributes to the advancement of hybrid hydrogen sensors and enhances our understanding of hydrogen sensing mechanisms.