Self-Powered All-Fiber Hydrogen Sensor via Whispering Gallery Mode Microcavity and Built-in Electric Field Synergy

Fiber-optic hydrogen sensors offer intrinsic safety and remote operation, yet their application is constrained by expensive spectrometers and complex demodulation. Here, we present a self-powered all-fiber hydrogen sensor (SAHS) that integrates optical excitation, electrical readout and gas detection on a single fiber tip, enabling remote and room-temperature sensing at zero bias. By constructing a whispering gallery mode (WGM)-enhanced lateral ZnO/PEDOT:PSS n-p heterojunction on the fiber tip, we achieve synergy between the localized optical field and the built-in electric field. The WGM microcavity confines and recycles incident light, markedly enhancing light-matter interaction and photogeneration on the tiny fiber tip. Meanwhile, the lateral built-in field efficiently dissociates the photogenerated carriers, producing a substantial photocurrent without any external voltage. The self-powered sensor exhibits outstanding room-temperature H2 detection under 380 nm light excitation upon Pd functionalization, with a detection limit of ∼19 ppm and response/recovery times of 30 s and 7 s, respectively. This light-activated, electrically-read-out architecture eliminates costly optical demodulation equipment, offering a low-cost, user-friendly and intrinsically safe solution for advanced hydrogen energy monitoring.