Synthesis of Vanadium Nitride by Nonisothermal Reduction and Nitridation with Ammonia Gas: A Combined Kinetics and DFT Study

Ammonia (NH3) is a potential carbon-free energy source. It can be used as a reducing and nitriding agent in the synthesis of vanadium nitride (VN). In this paper, non-isothermal kinetics and a microscopic reaction mechanism between vanadium oxide (V2O3) and NH3 were investigated. The activation energy was determined by using the KAS and FWO methods, averaging 83.05 kJ/mol. The results revealed that the reaction process consists three distinct stages based on the conversion ratio (α): α = 0–0.60, α = 0.60–0.87, and α = 0.87–0.95. The kinetic model functions were also established, and the whole reaction process was shifted from the deoxygenation stage to the nitridation stage. As the reaction proceeded, nitrogen atoms commenced replacing oxygen atoms within the lattice of VNxOy. The N content increased gradually, while the O content decreased correspondingly. Ab initio molecular dynamics simulations demonstrated that NH3 initially decomposed into NH2 and H atoms. The NH2 then forms stable V–N–V bonds with V atoms, while the released H atoms can react with the O atoms, potentially leading to the formation of H2O and the desorption of the O atoms. This research provides a more efficient and clean method for the preparation of VN.