Au-Doped V2O5 nanostructures for the low-temperature detection of SO2, NO2, C2H4, NH3, and CH4 with superior response to H2S using the reflux method

Pristine and Au-precursor (HAuCl₃) -doped V₂O₅ nanostructures were synthesised with varying Au-precursor concentrations (1, 3, 4, and 5 wt%) using a facile reflux method. XRD analysis revealed that all V₂O₅ samples exhibited an orthorhombic crystal structure, with crystallinity increasing as the Au-precursor concentration rose from 1 to 4 wt%. However, at 5 wt%, crystallinity was reduced, and a new peak emerged at 38.19°, corresponding to the (111) plane of Au. SEM imaging showed that doping transformed spherical V₂O₅ nanostructures into nanorod-like morphologies. EDS confirmed the presence of V, O, and Au, with nanorod diameters increasing alongside Au-precursor concentration. BET analysis indicated that all V₂O₅ samples exhibited Type IV isotherms, characteristic of mesoporous materials with high surface areas, which facilitated enhanced H₂S gas adsorption. FTIR spectroscopy verified the functional groups, while UV-vis spectroscopy analysed the optical absorption properties of both pristine and Au-doped V₂O₅. The gas-sensing performance was evaluated for H₂S concentrations ranging from 5 to 90 ppm at 150°C. Among the tested samples, S4-V₂O₅ (4 wt% Au-precursor doped) demonstrated the highest response to 90 ppm H₂S, outperforming undoped V₂O₅, S2-V₂O₅, and S3-V₂O₅. These results suggest that S4-V₂O₅ nanorods are a promising material for H₂S gas sensing applications.