Chemoresistive and Catalytic Dual-Signal Pd-WO3 MEMS Sensor for Reliable H2 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.