(396p) Solvation of Nitrogen in Metallic Vanadium: A Theoretical and Experimental Study

N₂-selective membranes could be useful in air separation, ammonia synthesis in addition to the post-combustion CO₂ capture. High partial pressure of N₂ especially in the post-combustion gas streams might have benefits against the conventional processes directly capturing CO₂. We suggest a vanadium(V)-based metallic membrane for N₂ separation. Solvation of N in V is critical to evaluate the membrane properties. Numerous V-N systems have been identified for application to the precipitate materials for strengthening steel products. However, no attempts have been made to calculate the solubility of mobile N for membrane applications.

Atomic N absorbed to the pure V metal could form a solid solution or induce a phase transformation to vanadium nitrides in varying temperatures. In contrast to the hydrogen solvation in palladium in a traditional H₂-selective membrane system, N binding in bcc V is much stronger and V lattice distortion is more significant due to the large atomic size of N. The interaction between N and V was investigated by first principles calculations based on density functional theory. The optimized geometry, binding energy and electronic structure after N absorption were calculated to deduce essential implications to the N solubility in V. The solubility can be computed across different V-N systems using grand canonical Monte Carlo simulation. In comparison to the theoretical investigation, solubility of N in V was measured experimentally using a gravimetric sorption analyzer. The comparison can verify the previously suggested solvation models and the model can be applied to predict the properties of the N₂-selective membrane.