Shape selective comprehensive gas sensing study of different morphological manganese-cobalt oxide based nanocomposite as potential room temperature hydrogen gas sensor

The design of morphology-based spinel structures has appeared as an effective approach for improving the performance of the sensor in hydrogen gas sensing to facilitate hydrogen economy. In this study, we report a detailed shape selective analysis of four different morphological spinel structures supported on reduced graphene oxide (rGO) as an efficient hydrogen sensor. Our study revealed that the response of manganese-cobalt oxides are strongly depended on the morphology of the system (flower, rod, flakes and sphere) which can be explained by combined effects of surface area, defects generated on the surface and crystallinity. The n-type responses of all native oxides and the composite modified with rGO indicated the formation of n-n heterojunction at their interface. The bare flower-like structure showed higher responses (S% = 6.3) with low response time (17 s) and recovery time (18 s) at higher temperature (160 °C). In comparison, the improved sensing behavior of the composite with highest response (12.77%) and lowest response-recovery time (9 s and 13 s, respectively) at room temperature can be attributed to the higher electrical conductivity of rGO with fast charge carrier mobility. Also, this novel gas sensor demonstrated superior sensitivity, higher stability, and better selectivity against various gaseous mixtures.