Chemoresistive and Catalytic Dual‐Signal Pd‐WO ₃ MEMS Sensor for Reliable H ₂ Monitoring

The demand for H₂ monitoring in its production and utilization grows rapidly to ensure operational efficiency and safety. Given the high flammability of H₂, it is crucial to detect levels below the lower flammability limit (4%) in a sensitive, rapid, and reliable manner. Although integrating multiple sensor types can improve selectivity and accuracy, such systems often involve bulky architecture and time-consuming operation. This study presents a dual-signal H₂ sensor based on a single microelectromechanical system (MEMS) platform, enabling miniaturization, low power consumption, and robust performance. Pd nanoparticle-decorated WO₃ nanorods (Pd-WO₃ NRs) are employed as sensing material and integrated into the MEMS substrate. The catalytic Pd promotes H₂ oxidation, enabling the sensor to simultaneously monitor resistance changes in the Pd-WO₃ NRs and temperature variations in the microheater. This dual-signal approach corresponds to concurrent chemoresistive- and catalytic combustion-type gas sensing. The sensor exhibits high sensitivity and selectivity toward H₂, with detection limits of 0.01%-0.02% for dual signals, and demonstrates excellent reliability under varying humidity levels, repetitive cycles, and static gas exposure conditions. This work provides a practical foundation for the development of single gas sensors with dual output signals, enabling robust and energy-efficient H₂ detection in diverse environmental and industrial scenarios.