Effect of Salt Content and Operating Temperature on the Nitrogen Dioxide Gas Sensing Performance of Sodium-Ion Conducting Solid Polymer Electrolyte

Abstract

Sodium-ion conducting solid polymer electrolyte (Na-SPE) films based on polyvinyl alcohol (PVA) with various weight percentages of sodium iodide (NaI) were prepared using the casting technique. The films’ structural, morphology and electrical conductivity were examined to understand the sensing mechanism of the as-prepared Na-SPE films. The X-ray diffraction (XRD) and atomic force microscopy (AFM) data, respectively, showed the amorphous and homogeneous granular structure of Na-SPE films due to the high dissociation of NaI in the PVA matrix for all concentrations. The changes in the FTIR vibrational modes of Na-SPEs provide evidence of interactions between cations and functional groups of the host matrix. The effect of salt content, operating temperature and gas concentration on the performance of the Na-SPE sensor towards NO2 were investigated. In contrast to the pure PVA film, which did not respond to NO2 gas at low concentrations, Na-SPE films exhibit higher sensitivity to NO2 gas with faster response and recovery times. At low NO2 gas concentration (50 ppm), a sample containing 20 wt.% of NaI exhibits the highest sensitivity at the operating temperature of 200 °C. In comparison, at a high NO2 gas concentration (550 ppm), a sample containing 40 wt.% of NaI exhibits a maximum sensitivity at 150 °C. These findings suggest that Na-SPE films would be suitable for gas sensor applications. HIGHLIGHTS Na-SPEs films based on PVA with various salt contents have been prepared using the casting method The Hall effect data confirm the n-type conductivity of the Na-SPEs Na-SPE structure exhibits high sensitivity towards NO2 with rapid response/recovery times SPE film has a maximum sensitivity of 127.3 % at low NO2 gas concentration and a maximum sensitivity of 126 % at high gas concentration These results imply that this compound would be suitable for environmental and industrial uses GRAPHICAL ABSTRACT