Detection of Xylene Using Ni(OH)2-Enhanced Co3O4 Nanoplate via p–n Junctions

This study reports a novel Ni(OH)2/Co3O4 heterostructured nanomaterial synthesized through a simple two-step hydrothermal method combined with subsequent heat treatment. The Ni(OH)2/Co3O4 heterostructured nanomaterial showed excellent performance in the detection of xylene gas. XRD, SEM, and EDS characterized the crystal structure, microstructure, and composition elements of Co3O4 and Ni(OH)2/Co3O4, and the gas sensing properties of the Co3O4 sensor and Ni(OH)2/Co3O4 sensor were systematically tested. The test results indicate the Ni(OH)2/Co3O4 sensor has an optimal operating temperature of 175 °C, which is 10 °C lower than that of the Co3O4 sensor; has a response of 14.1 to 100 ppm xylene, which is 7-fold higher than that of the Co3O4 sensor; reduces the detection limit of xylene from 2 ppm to 100 ppb; and has at least a 4-fold higher response to xylene than other gases. The Ni(OH)2/Co3O4 nanocomposite exerts the excellent catalytic performance of two-dimensional nanomaterial Ni(OH)2, solves the deficiency in the electrical conductivity of Ni(OH)2 materials, and realizes the outstanding sensing performance of xylene, while the construction of the p–n heterojunction between Ni(OH)2 and Co3O4 also improves the sensing performance of the material. This study provides a strategy for designing high-performance xylene gas sensors using two-dimensional Ni(OH)2 materials.