Selection of Surface Coatings for High H2 Permeability Group 5 Metal Membranes Using First-Principles Calculations

To select useful surface coatings for high H2 permeability metal membranes, the hydrogen transport properties in composite membranes of V, Nb, and Ta coated with different transition-metal carbides (TMCs) (TM = Ti, Hf, Zr) have been systematically investigated using first-principles calculations together with statistical mechanics methods. These calculations were used to predict the hydrogen flux and characterize the diffusion resistances in these composite materials. Our results indicate that the coating material on the permeate side controls the net H2 flux at low temperature, where the H2 desorption energies on the surfaces of the membrane coating are important. At sufficiently high temperature, H diffusion through the membranes controls the net flux. Overall, our results predict that TiC is the best coating and TiC/V/TiC is the best composite membranes among the materials studied.