First principles investigation of metal sulfides as membranes in hydrogen purification

Degradation of metal membranes by sulfur in high temperature hydrogen purification is an important challenge in practical use of these membranes. If metal sulfides could be identified with high hydrogen permeabilities, they could potentially sidestep the difficulties faced by metal membranes. We have used first principles calculations to predict the permeability of hydrogen through eight metal sulfides in their defect-free, crystalline form. Although the solubility of H in some of these materials is considerable, H diffusion is extremely slow in every case. Our calculations indicate that films of any of the sulfides we considered will have extremely low permeabilities for hydrogen.