Ammonia gas sensing characteristics of V2O5 nanostructures: A combined experimental and ab initio density functional theory approach

Abstract

A combined experimental and density functional theory study of NH(sub3) gas sensing and adsorption characteristics of a-V(sub2)O(sub5) synthesized from hydrated NH4VO3 in CVD at 400 °C (in N(sub2) for 12 and 24 h.) is presented. Highly crystalline orthorhombic a-V(sub2)O(sub5) nano-rods with dominant (001) and (110) planes/facets nano-rods were observed from XRD, SEM and TEM characterizations. Using VSM technique, para- to ferro- magnetic transition was observed in the a-V(sub2)O(sub5) nanoparticles synthesized at 24 h. Improved gas sensing was observed in case of paramagnetic a-V(sub2)O(sub5) nano-rods (nanoparticles synthesized at 12 h.) compared with the one synthesized at 24 h. Additionally, significant rise in gas sensing response was observed around the metal to insulator transition temperature. Calculation of adsorption of NH(sub3) molecule(s) on (001), (110), (200) and (400) facets showed that (001), (200) and (400) possessed more active sites than (110) surface. DFT calculations were also used to investigate NH3 adsorption on (110) surface of a-V(sub2)O(sub5) with the analysis showing exponential decrease in the electronic band gap of the material’s surface with the increasing numbers of NH(sub3) loadings.