AC characterization of nitrate intercalated layered double hydroxides gas sensors

Layered Double Hydroxides nanostructures and their possibility of accommodating different molecules or atoms inside their matrix bestow a large number of interesting physical and chemical properties. Indeed, these materials have been widely used for different purposes. Nevertheless, their usage in gas sensors applications is still challenging since Layered Double Hydroxides conduction mechanisms are not completely clear. To this purpose, ac impedance spectrum analysis can represent a powerful technique to investigate specific conduction mechanisms. In fact, ac characterization allows highlighting the different contributions of the conduction and it permits to find out information about the undergoing physical phenomena. In this work, a fully ac characterization of a Nitrate-intercalated Zn/Al Layered Double Hydroxides gas sensor such as is performed. In particular, the complex impedance of the sensor is measured in the range 1 Hz to 100 kHz in presence of different concentrations of three volatile compounds (CH4, CO2 and NO). The Nyquist plots show an evident variation of sensor impedance when sensor is exposed to the gas. Finally, a circuital model of the sensor that takes into account the peculiar conduction processes is introduced to fit the experimental data and explain the sensor behavior.