Three-dimensional CoS1.097/Al2O3 composites assembled with ultra-thin nanosheets for high-performance NOx gas sensing at room temperature†

A simple hydrothermal method combined with a self-sacrificial template was utilized to synthesize three-dimensional hierarchical CoS_1.097/Al₂O₃ microflowers (CAS MFs). The CAS MFs were assembled by stacking ultra-thin nanosheets (NSs) (average thickness of approximately 6 nm), which were derived from cobalt aluminum layered double hydroxides (CoAl-LDHs, named as CA). In detail, CoAl-LDHs were chosen as the self-sacrificial template, the sublimed sulfur powder was used as the sulfur source, and vulcanization via chemical vapor deposition (CVD) was performed to synthesize CoS_1.097 nanocrystals (NCs) distributed on the surface of CAS. The as-prepared CoS_1.097/Al₂O₃ composites exhibited a 3D hierarchical structure with an abundant microporous structure. Furthermore, CAS-6 (which was synthesized under optimal conditions) showed an excellent response of 30.1 (S = R₀/R_g), a response/recovery time of 1.3 s/13.3 s to 100 ppm NO_x at room temperature (RT) and a low detection limit of 10 ppb. The superior gas sensing performance was mainly due to the 3D hierarchical and abundant microporous structures and uniform distribution of CoS_1.097 NCs on the surface of the CAS MFs. This outstanding gas sensing performance of CAS-6 indicates its potential to be used as gas sensor at RT.