Sensing Performances of Hierarchical Nano-Layered V₂O₅ Structures and <em>Ab Initio</em> Calculation of Their Gas-Adsorption Properties

Significant research efforts have recently focused on nanomaterial processing for gas sensors and related sensing applications. However, the major challenges in the field involve the choice of material for the sensing layer of the sensor device element together with the right structure, assembly, and morphology through which the full sensing properties of the material can be realised. Herein, we critically review the hierarchical nanostructures of V2O5 nanomaterial for application in gas sensing technology. Beyond the sheet structure which serves as the fundamental building block of the V2O5’smolecular arrangement, Nanostructures ranging from nanobelts to nanowires, nanorods, nanoribbons, nanofibers, nanotubes, and thin films were discovered as preferred configuration and thermodynamically favorable structures – according to many synthesis processes. Ethanol (C2H5OH) and Nitrogen dioxide (NO2) gases were identified as preferred molecules commonly detected by various V2O5 morphologies, with the nanotube structure showing preferential sensitivity and selectivity to C2H5OH. We also discuss perspectives from density functional theory (DFT) studies of V2O5 nanostructures and other (2D) materials structures for gas sensing applications. The studies highlight enhanced adsorption energy, increase conductivity, and band gap variation as a result of an upper shift in Fermi level, all as consequence of surface interaction between semiconductor crystal orientation and chemical molecules. Finally, our calculations of the optimised parameters for α-V2O5 orthorhombic structure showed good agreement with experimental and other theoretical data in the literature. The adsorption energy profile for NO2 molecules revealed that Ag-doped surface exhibits the most negative adsorption energy compared with the clean surface and other doped surfaces.