Fast and Highly Sensitive H ₂ Sensor Based on Ag‐Modified ZnO Nanoflowers

Rapid and sensitive detection of trace‐level H ₂ is essential for hydrogen energy safety and industrial monitoring, yet remains challenging. Herein, Ag‐modified ZnO nanoflowers are developed for fast and ultrasensitive H ₂ sensing. Structural and surface analyses reveal that Ag forms Schottky contacts with ZnO and significantly promotes the generation of active oxygen species. The optimized Ag–ZnO sensor exhibits a high response of 59.4 toward 100 ppm H ₂ at 275 °C, which is approximately 13.5 times higher than that of pristine ZnO (4.4), together with an ultrafast response time of 4  s and a theoretical detection limit of 5.1 ppb. Moreover, the sensor demonstrates excellent repeatability, long‐term stability, and high selectivity against common interfering gases. The enhanced sensing performance originates from the synergistic effects of Schottky junction‐induced resistance modulation and oxygen species‐mediated surface reaction enhancement, where Ag increases the baseline resistance and facilitates H ₂ oxidation. This work provides an effective strategy for constructing high‐performance ppb‐level H ₂ sensors with potential applications in hydrogen safety monitoring and energy‐related systems.