High-Sensitivity Room-Temperature Micro-Electro-Mechanical System Calorimetric Hydrogen Sensor Enabled by the Palladium Metallene Catalyst

The safe deployment of hydrogen (H 2 ) energy requires highly sensitive sensing technologies that eliminate intrinsic ignition risks. Herein, this work reports a high-performance room-temperature calorimetric H 2 sensor, achieved through the synergistic integration of a highly sensitive single-crystal silicon micro-electro-mechanical systems (MEMS) thermopile with a two-dimensional (2D) Pd metallene catalyst. The ultrathin thickness and defect-rich structure of the Pd metallene provides exceptional catalytic activity for ambient hydrogen oxidation to water, a mechanism directly visualized by in situ Raman microspectroscopy, while the MEMS thermopile efficiently transduces the generated reaction heat into an electrical signal. Compared to sensors employing traditional Pd nanoparticles, the 2D Pd metallene-based device exhibits a remarkable 690-fold enhancement in response signal, alongside significantly accelerated response/recovery kinetics (response/recovery time: ∼3 s). The sensor demonstrates outstanding comprehensive performance, including an extremely low detection limit (<25 ppb), a wide linear detection range (25 ppb to 2%), good selectivity, minimal power consumption (∼4 mW), and long-term stability. This work not only elucidates the superior catalytic properties of 2D Pd metallenes for room-temperature hydrogen oxidation but also establishes a new pathway for developing ultralow-power, high-performance H 2 sensors for safety-critical applications.