Interfacial stress decoupling enables stable palladium-based hydrogen sensing

Interfacial adhesion between the sensing layer and supporting substrate critically governs the long-term stability of electrical molecular sensors. However, achieving a robust heterointerface remains challenging due to the intrinsic lattice mismatch induces localized stress, which is further exacerbated by cyclic interactions between the sensing film and gas analytes. Here, we introduce a floating-structure palladium hydrogen (H₂) sensor enabled by interfacial stress decoupling through a dithiol-based self-assembled monolayer (SAM). This interfacial layer acts as a molecular bridge between the palladium sensing layer and the substrate electrode, forming a dual-interface architecture that simultaneously mitigates the interfacial stress and suppresses the substrate clamping effects, thereby accelerating H₂ absorption kinetics. The resulting sensor demonstrates a stable and cyclable H₂ detection at concentrations up to 4 vol%, and an ultrasensitive detection limit of 1 ppm at room temperature. Moreover, we realize wafer-scale fabrication and integration of the sensor into a portable platform for real-time hydrogen leak detection. This interfacial stress-engineering approach provides a general route toward durable and high-performance molecular sensor.