Metal-Organic-Framework-Derived Hollow In2O3 Microtubes with Bimetallic PdPt Alloy: Fast Trace Hydrogen Sensing with Suppressed Response Inversion

Palladium (Pd)-based sensitizers are widely employed to boost the hydrogen (H2) sensing properties of metal oxide semiconductor (MOS)-based sensors owing to their outstanding catalytic activity. However, the generation of palladium hydride (PdHx) induces strong electron scattering, causing an abnormal response inversion that compromises detection reliability. Herein, we proposed an electronic structure engineering induced by alloying to suppress response inversion. Metal-organic-framework-derived In2O3 hollow microtubes decorated with PdPt alloy were assembled into sensor devices and evaluated for H2 detection. The sensor with 0.5 wt.% PdPt loading achieves the optimal performance, with high sensitivity (9.5 to 100 ppm H2), ultrafast response/recovery kinetics (3 s/4 s), and a limit of detection as low as 500 ppb. Notably, the PdPt/In2O3 sensor completely eliminates abnormal response inversion in contrast to the Pd/In2O3 sensor. Density functional theory calculations reveal that the modification of the PdPt alloy preserves high catalytic activity toward H2 while effectively hindering the diffusion of H atoms into the Pd bulk, thereby ensuring sensitive and reliable sensing. Furthermore, the PdPt/In2O3 sensor array integrated with machine learning algorithms demonstrates reliable discrimination of H2 from interfering gases, highlighting its potential for practical gas monitoring. This study provides a rational electronic structure engineering strategy to suppress PdHx-induced response inversion, providing a clear experimental and theoretical foundation for the development of reliable H2 sensors.