In-situ sulfidation-derived three-dimensional cobalt sulfide nanoflower/graphene nanosheet hybrid for ultrasensitive room-temperature NO2 gas sensor

Two-dimensional (2D) nanosheets show great potential for gas sensing, but they can hinder the penetration of gas molecules and lead to deteriorated sensing performances. Hence, construction of 2D nanosheet-based gas sensing materials with unique structures is desirable for high-performance gas sensing. Herein, a three-dimensional (3D) binary nanosheet heterostructure based on 3D cobalt sulfide (CoS) nanoflower/graphene nanosheet hybrid was constructed for room-temperature NO2 gas sensing. The 3D CoS/reduced graphene oxide (rGO) hybrid derived from a mixture of Co3O4 nanoflowers and graphene oxide nanosheets was facilely formed via in-situ sulfidation and reduction processes. The resistance response of as-assembled gas sensor based on 3D CoS nanoflower/graphene nanosheet hybrid to 1 ppm NO2 was 39.7%, which was 4.2 and 3.1 times higher than that of CoS and rGO sensors, respectively. A response as high as 10.5% was achieved even when the device was exposed to NO2 gas with a low concentration of 50 ppb. Furthermore, the hybrid device exhibited linear response characteristic, high selectivity, good repeatability, as well as long-term stability. Overall, the proposed design strategy together with the as-constructed structures can pave the way for the development of high-performance gas sensors based on graphene hybrids.