Fast Selective Sensing of Nitrogen-Based Gases Utilizing δ-MnO2-Epitaxial Graphene-Silicon Carbide Heterostructures for Room Temperature Gas Sensing

Real-time toxic gas mapping in complex urban environments have become increasingly possible with improvements in data analysis and network infrastructures. Hindering this is the cost and operation requirements of commercial gas sensors, requiring sensors with high sensitivity and selectivity that are robust and capable of operating at room temperature. Transition metal oxide-based sensors are of historical significance in the production of commercial gas sensors due to their low cost and high selectivity to target gases. The low inherent conductivity of metal oxides, however, requires operating temperatures higher than 150 °C, limiting their operation to controlled environments. To overcome this limitation, heterostructures have been formed between graphene and transition metal oxides, seeking to couple the conductivity of graphene with the reactivity of transition metal oxides. Among these transition metal oxides, manganese dioxide exhibits unique properties that can be leveraged to improve gas sensing. Its wide variety of synthesized structural polymorphs (1 × 1 tunnel (β), 1 × 2 tunnel (α), spinel (y), and layered (δ)) allow for control over the available reactive surface area to enhance gas response. By utilizing defect rich δ-phase, the reactivity of the material can be improved. Here we present a δ-MnO
₂
/epitaxial graphene/silicon carbide heterostructure for use as a room temperature gas sensor. We confirm the composition through Raman spectroscopy and surface morphology through scanning electron microscopy and atomic force microscopy. We then demonstrate its room-temperature detection by testing against NO
₂
, NH
₃
, IPA, and CH
₃
OH at room temperature.