XPS and Kelvin probe studies of SnO2/RGO nanohybrids based NO2 sensors

Abstract

The present paper reports the successful detection of NO2 using the hydrothermally synthesized SnO2/RGO nanohybrids. The nanohybrids successfully detected NO2 below its threshold limit value (TLV) with a minimum detection limit of 0.5 ppm. The 3-fold sensor response (Rg/Ra) was obtained towards 3 ppm of NO2 at an operating temperature of 200 °C. Importantly, the nanohybrids exhibited faster response kinetics. For example, the response and the recovery times of 10 and 40 s, respectively were obtained for 1 ppm NO2 exposure. In nanohybrids, the particle size of SnO2 is ~5–7 nm which is comparable to twice of its Debye length (3 nm) and accordingly, benefits the charge transport and the sensor response. NO2 adsorption on the sensor surface is further studied using the Elovich model. The obtained results were further corroborated with the observations from X-ray photoelectron spectroscopy (XPS) and Kelvin probe studies performed before and after exposure to NO2. The considerable long-term stability and selectivity indicate that the developed sensor can find a promising application in NO2 detection.