Shape Selective Comprehensive Gas Sensing Study of Modified rGO with Different Morphological Manganese-Cobalt Oxides as Potential Room Temperature Hydrogen Gas Sensor

Abstract

Hydrogen (H2) has been considered as a worth choice for the fuel generating resource to produce clean energy for globally accepted practice because of their zero emission to get pollution free green environment by slowing down the rapid consumption of hydrocarbons from industrial setups as well as from transportations1. Despite of effectual usefulness, safety is one of the major issue for this gas because of its flammable and explosive nature in open atmosphere. Therefore, monitoring of level of concentration has become an essential factor to avoid any unpredictable accidents in natural atmosphere during the consumptions, productions and storage of the gas. In addition, the detection of minimal concentration of H2 with fast and more accuracy in sensitivity has become the top most priority for developing any sensor devices. The design of morphology-based spinel structures have appeared as an effective approach for improving the performance of the sensor in hydrogen gas sensing to facilitate hydrogen economy2,3. Towards this context, we report a detailed shape selective analysis of four different morphological spinel structures supported on reduced graphene oxide as an efficient hydrogen sensor. The structural confirmation of the synthesized materials were determined by highly advanced characterization techniques like Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, Powder X-ray diffraction (PXRD), UV-visible spectroscopy (UV-Vis), X-ray photoelectron spectroscopy (XPS), Transmission electron microscopy (TEM), Scanning electron microscopy (SEM), photoluminescence study and N2 adsorption-desorption analysis. 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 and the defects generated on the surface on the oxides. The n-type responses of all native oxides and the composite modified with reduced graphene oxide indicated the formation of n-n heterojunction at their interface. The bare flower-like manganese-cobaltite structure showed higher responses (6.8%) due to their highest surface defects as well as larger surface area along with lower response (17 s) and recovery time. Such improved sensing behavior of the composite with highest percentage of response (12.77%) and lowest response as well as recovery time at room temperature can be attributed to the higher electrical conductivity of rGO along with fast charge carrier mobility. In Overall, this novel gas sensor demonstrated superior sensitivity, higher stability and better selectivity against various gaseous mixtures.