High selectivity and response H2 sensors based on ZnO@ZIF-71@Ag nanorod arrays

Hydrogen (H2) is widely used in industrial and medical, however its flammable and explosive nature requires economical and effective monitoring to ensure safety. In this work, ZnO@ZIF-71@Ag nanorod arrays were synthesized to provide an effective adsorption response to H2 through size effect and high catalytic activity by immobilizing Ag nanoparticles (NPs) into the pores of ZIF-71. The results of the gas sensitivity tests showed that the nanorod arrays were significantly more selective towards H2. Moreover, the response of ZnO@ZIF-71@Ag to 50 ppm H2 was 11 times higher than that of ZnO@ZIF-71 at a lower operating temperature (150 degrees C). The size of the Ag NPs was demonstrated to be below 10 nm by TEM characterization, suggesting that Ag in the form of quantum dots (QDs) to bring an unignorable catalytic effect for breaking hydrogen molecule (H2) into highly active atoms ([H]). In addition, the result of Density Function Theory (DFT) calculation revealed that the adsorption energy of Ag-catalyzed [H] (-8.255 eV) was much higher than that of H2 (-4.222 eV) on ZnO (100), which results in elevated charge transfer to promote hydrogen sensing performance of ZnO@ZIF-71@Ag. In this study, a novel hydrogen sensor based on pore sieving and catalytic sensing mechanisms was obtained, which provides a new reference for the development of hydrogen sensors.