Enhancing nitrous oxide chemiresistive sensing performance by reducing ionic Oxygen species adsorption in Gold functionalized Tungsten Trioxide nanofibers

Low-cost nitrous oxide (N2O) gas sensor is in great need to provide real-time information to various stakeholders. Herein, various gold functionalized tungsten trioxide nanofibers (Au-WO3 NFs) with different composition and crystallinity were synthesized by controlling electrospinning solutions and post heat treatment. These sensing materials were systematically exposed to various N2O concentrations at different operating temperatures (i.e., 250 to 450 °C). Among different samples, 1 at % gold functionalized WO3 nanofibers (1 at % Au-WO3 NF) annealed at 600 °C for 24 h shows the highest sensitivity (S = Ra/Ro) of 38.5 toward 100 ppm at 250 °C with experimentally determined limit of detection (LOD) at 2.5 ppm. Although recovery and recovery time improved, the sensitivity reduced with an increase in operating temperatures. The detailed sensing mechanism studies indicated that the high N2O sensing was achieved when there were limited adsorbed ionized oxygen species (e.g., O-). Moreover, N2O adsorption and desorption activation energy were estimated to be 0.13 and 0.87 eV where desorption was more strongly temperature dependent than adsorption.