A Self‐Powered, Ultrasensitive, and Flexible Gas Sensor Based on Tough and Degradable Leather Hydrogel for Portable Wireless Trace H 2 S Detection

ABSTRACT Hydrogen sulfide (H 2 S), a toxic gas and key biomarker, is crucial to environmental safety and human health, yet existing sensors struggle with real‐time, portable detection at trace levels. Here, we report a cost‐effective, flexible, self‐powered H 2 S sensor with outstanding performance at room temperature, constructed using a galvanic cell structure and leather hydrogel as the electrolyte. The degradable, tough leather hydrogel confers flexibility, mechanical robustness, and eco‐friendliness on the sensor. Upon gas adsorption, monitoring the electrode potential change induced by interfacial charge transfer enables a pronounced response even to trace concentrations. The sensor delivers exceptional sensitivity, with a detection limit down to 0.109 ppb—the lowest among reported electrochemical H 2 S sensors—while also exhibiting excellent selectivity, stability, and repeatability. Performance can be further enhanced by serially connecting, and its self‐powered nature enables visual detection of H 2 S concentration. Furthermore, a wireless sensing system based on Bluetooth and cloud technology is developed, validating the sensor's practical application potential in periodontitis grading diagnosis, meat spoilage monitoring, and H 2 S leak detection. This work provides a novel strategy for the development of high‐performance, cost‐effective, portable H 2 S sensors and holds great promise for applications in environmental monitoring, health diagnostics, and smart sensing systems.