Dimensionality regulation of ZIF anti-interference layer for high-selectivity and fast-response hydrogen sensing

In this paper, the Zeolitic imidazole framework (ZIF) is designed and synthesized as the anti-interference layer of the Palladium-Nickel (PdNi) alloy thin-film coated surface acoustic wave (SAW) hydrogen (H-2) sensing device. Dimension regulation of the ZIF is conducted to obtain superior interference immunity. The two-dimensional (2D) and three-dimensional (3D) ZIF are prepared on top of PdNi thin-films by drop-coating. The gas experimental results indicate that 2D ZIF@PdNi sensors are more sensitive than 3D ZIF@PdNi and pure PdNi. At ambient temperature (25 degrees C), a fast response/recovery time of 12.03/14.62 s towards 8% H-2 gas, an ultralow limit of detection of 5 ppm, and a significantly increased sensitivity of 16.77 mV/% are achieved. Additionally, the 2D ZIF@PdNi sensors feature outstanding selectivity for H-2 gas against other gases (CO/NH3/H2S), good reversibility, and long-term stability for 30 days. The improved H-2 sensing performance can be attributed to that the two-dimensional anti-interference layer (2D ZIF) is more conducive to the diffusion of gas molecules, which in turn increases the interaction between PdNi and the target gas.