Defect-Engineering of 2D Dichalcogenide VSe₂ to Enhance Ammonia Sensing: Acumens from DFT Calculations

Opportune sensing of ammonia (NH₃) gas is industrially important for avoiding hazards. With the advent of nanostructured 2D materials, it is felt vital to miniaturize the detector architecture so as to attain more and more efficacy with simultaneous cost reduction. Adaptation of layered transition metal dichalcogenide as the host may be a potential answer to such challenges. The current study presents a theoretical in-depth analysis regarding improvement in efficient detection of NH₃ using layered vanadium di-selenide (VSe₂) with the introduction of point defects. The poor affinity between VSe₂ and NH₃ forbids the use of the former in the nano-sensing device's fabrications. The adsorption and electronic properties of VSe₂ nanomaterials can be tuned with defect induction, which would modulate the sensing properties. The introduction of Se vacancy to pristine VSe₂ was found to cause about an eight-fold increase (from -012 eV to -0.97 eV) in adsorption energy. A charge transfer from the N 2p orbital of NH₃ to the V 3d orbital of VSe₂ has been observed to cause appreciable NH₃ detection by VSe₂. In addition to that, the stability of the best-defected system has been confirmed through molecular dynamics simulation, and the possibility of repeated usability has been analyzed for calculating recovery time. Our theoretical results clearly indicate that Se-vacant layered VSe₂ can be an efficient NH₃ sensor if practically produced in the future. The presented results will thus potentially be useful for experimentalists in designing and developing VSe₂-based NH₃ sensors.