The effects of Ag concentration on toluene gas sensing performance of Ag NPs decorated on g-C3N4 sheets

In this study, Ag nanoparticles (NPs) were decorated on graphitic carbon nitride (g-C3N4) sheets with different concentrations of Ag (1%, 3%, and 5%) using a co-precipitation method as a selective toluene gas sensor. The X-ray diffraction (XRD) patterns of the samples indicated that Ag NPs did not affect the phase of the g-C3N4 nanocomposites. The Ag NPs were well dispersed on the g-C3N4 sheets, as shown by transmission electron microscopy (TEM) images. The optical characterization results revealed that Ag NPs decreased the bandgap of g-C3N4 nanocomposites. The results of gas sensing indicated that compared to the pristine g-C3N4 sheets, sensors based on Ag NPs decorated g-C3N4 sheets exhibited a stronger response to toluene due to the formation of more defects and active sites on the surface of g-C3N4 sheets. Moreover, the 5%Ag/g-C3N4 nanocomposite exhibited the highest response and selectivity to 50 ppm toluene at 200 °C (25.4% and 61.3%, respectively). In addition, 5%Ag/g-C3N4 nanocomposite demonstrated a faster response/recovery time and superior long-term stability than the other sensors.