Study on highly selective sensing behavior of ppb-level oxidizing gas sensors based on Zn2SnO4 nanoparticles immobilized on reduced graphene oxide under humidity conditions

Abstract

Highly selective oxidizing gas sensors are of great importance for environmental pollution monitoring. In this work, a hybrid material containing Zn2SnO4 nanoparticles (NPs) and immobilized reduced graphene oxide (Zn2SnO4-RGO) was developed as a high performance gas sensing material for the detection of ppb-levels of oxidizing gases (NO2 and O3). The structural, morphological and compositional properties of the Zn2SnO4-RGO hybrids were systematically characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS), which demonstrated the successful anchoring of Zn2SnO4 NPs on RGO nanosheets. The obtained Zn2SnO4-RGO hybrids exhibited outstanding sensing performance for detecting oxidizing gases (NO2 and O3) with very low cross sensitivities to reducing gases, such as C2H5OH, CH3COCH3 and CO. The Zn2SnO4-RGO based sensors exhibited high response values of up to 3.50 for 500 ppb NO2, which is higher than that for detection of 500 ppb O3 (1.78) at 30 °C under 50% relative humidity (RH). Moreover, the NO2 sensing performances of Zn2SnO4-RGO-based sensors were investigated under various RH. In all cases, the sensors based on RGO and Zn2SnO4-RGO hybrids presented p-type behavior. The sensors based on Zn2SnO4-RGO hybrids also exhibited high response values of up to 3.62 for 1 ppm NO2 at 50 °C in 80% RH, which is much higher than that of pure RGO (1.31). The excellent sensing performances are mainly ascribed to the synergetic effect of Zn2SnO4 NPs and RGO. Furthermore, the surface reaction between Zn2SnO4-RGO hybrids and NO2 can be concluded from Operando diffuse reflectance infrared Fourier transformed spectroscopy (Operando DRIFT).