Extremely Sensitive and Selective NO2 Detection at Relative Humidity 90% in 2-Dimensional Tin Sulfides/SnO2 Nanorod Heterostructure

Abstract

The heterostructure between two-dimensional (2D) metal sulfides and metal oxides is one of the effective strategies to enhance the gas sensing performance owing to their unique electronic properties at the interfaces. In this study, we focus on enhancing gas sensing response under highly humid conditions using 2D tin sulfides (SnS and SnS2)-SnO2 heterostructures in form of vertically aligned 1D nanostructures. They exhibit superior gas response and recovery to 1 ppm NO2 under 90% of relative humidity (RH90) with an extremely low theoretical detection limit of 1.67 ppt. Furthermore, we demonstrate the gas sensor arrays using noble metal catalyst decoration which exhibit diverse selectivity toward various gases. We simulate the gas adsorption/desorption mechanism to reveal the mechanism of gas sensing properties of sulfurized SnO2 NRs under RH90. As a result, a higher preference of H2O physisorption over chemisorption by tin sulfides provided empty active sites even under RH90, yielding higher gas response than pristine SnO2 whose active sites are fully occupied by H2O under RH90. This work will provide a new perspective to the development of gas sensors suitable for high RH conditions like the examination of exhaled breath.