Detection of NOx down to ppb levels at room temperature based on highly mesoporous hierarchical Ni(OH)2–In(OH)3 double hydroxide composites

The 3D flower-like mesoporous hierarchical architecture materials were fabricated via a facile one-pot reflux method. The composites were carefully characterized by XRD, SEM, BET, XPS, EIS and MS plot measurements. The results indicated that the morphology of the obtained products could be controlled by adjusting the reaction time, and the sample with the mass ratio of 30 % In(NO 3 ) 2 ·6H 2 O/Ni(NO 3 ) 2 ·6H 2 O (labeled as NIDH-30) formed 3D flower-like mesoporous hierarchical architecture, which was composed of nanopetals with porous thin nanosheets and the size of In(OH) 3 nanoparticles around 8–13 nm. As a result, NIDH-30 exhibited excellent sensing properties at ultra low detection limit of 9.7 ppb for detection of NO x . The response toward 97 ppm NO x could reach to 60 % and the response time was 1.2 s. Moreover, it showed a great selectivity and stability at room temperature. The excellent gas sensing performance could be ascribed to higher surface area and space-charge layer which induce the highly effective surface interaction between the target gas molecules and the surface active sites. Synergetic effect and electronic effect also favoring the effective adsorption of NO x on the surface. All the factors were obviously beneficial for the mesoporous hierarchical Ni(OH) 2 –In(OH) 3 double hydroxide composites as gas sensor for monitoring air pollution.