Highly mesoporous hierarchical nickel and cobalt double hydroxide composite: fabrication, characterization and ultrafast NOx gas sensors at room temperature

Abstract

In this paper, highly mesoporous hierarchical nickel and cobalt double hydroxide composites (NCDHs) have been synthesized via a simple reflux method. The synthesized NCDH composites with a mass ratio of 100 : 20 for Ni(NO₃)₂·6H₂O/Co(NO₃)₂·6H₂O (NCDH-20) contained a lot of oxygen defect sites, and chemisorbed water connects the adjacent Ni(OH)₂ layers. The porous hierarchical nanostructures provide natural channels for the effective and fast transportation of carriers. Furthermore, the NCDH-20 sensor exhibits excellent gas-sensing properties, such as a low detection limit of 0.97 ppm and short response time of 0.6 s to 97 ppm NO_x, due to the layered single crystal structure and unique gallery pathway. The NCDH-20 sensor with ultrafast NO_x sensing has significant applications for gas sensing.