Palladium Nanoparticles Modification endowing ZIF-67@ZIF-8 with Rapid Hydrogen Gas Response at Low Operating Temperature

H 2 gas sensors with facile preparation, high sensitivity and low detection limits are crucial for hydrogen energy safety. Given the high surface area, abundant porosity and high stability, zeolitic imidazolate frameworks (ZIFs) provide a potential development path for hydrogen sensors. In this work, ZIF-67@ZIF-8 modified with palladium nanoparticles (Pd NPs) was synthesized by room-temperature solution synthesis and NaBH 4 reduction method. The xPd@ZIF-67@ZIF-8 (x=10, 20, 30, 40) samples exhibit a rough mesoporous surface due to etching of NaBH 4 and feature a uniform distribution of Pd NPs. The modification of Pd NPs broadens the hole accumulation layer (HAL) of ZIF-67@ZIF-8 and decreases the resistance (from ~500 to 1 MΩ), thereby reducing the operating temperature. It is noteworthy that the operating temperature zone of 20   Pd@ZIF-67@ZIF-8 is 85-115 ℃ with higher hydrogen sensitivity than the other sensors at optimum operating temperature (≥ 100 ℃). Meanwhile, the 20   Pd@ZIF-67@ZIF-8 sensor demonstrates a rapid response speed to low concentration H 2 (response to 50 ppm H 2 within 8 s) on account of the spillover and catalytic effects of Pd NPs. Furthermore, the 20   Pd@ZIF-67@ZIF-8 sensor possesses a relatively low theoretical detection limit (16.5 ppb), and exhibits excellent moisture resistance, cycle and long-term stability. This sensitive material provides a prospective avenue for hydrogen energy safety monitoring.