CeO 2 /Ni-Al layered double hydroxide composite as a gas sensor for volatile organic compounds detection

Layered double hydroxides (LDHs), having two efficient properties of gallery pathway and memory effect, are new functional materials that are associated with challenges to be present in the field of gas sensors. It is possible to say that the most important weakness of these structures is low electrical resistance. The proposed solution is to create a heterojunction with metal oxide semiconductors. In this regard, (CeO2)x/Ni-Al LDH composites were prepared based on ceria nanorods in three different size during hydrothermal and co-precipitation processes. The microstructure and morphology of the samples were examined and evaluated by FESEM, HRTEM, EDS, EDS mapping, XRD, MS, and XPS. The sensing properties of the samples were investigated under operating conditions: room temperature (25degree celsius), and relative humidity (40 % RH) with selected volatile organic compounds (methanol, ethanol, and acetone) in the concentration range of 25-300 ppm. According to the obtained results, the (CeO2)3/Ni-Al LDH composite response to methanol, ethanol, and acetone was 20.08 +/- 0.17, 26.54 +/- 0.22, and 7.15 +/- 0.12, respectively. Functional parameters were measured and analyzed including response/recovery times, repeatability, stability, selectivity, LOD, LOQ, R2 and RSD%. Finally, the response mechanism was investigated based on the n-n heterojunction theory.