Development of Nb35Mo5Ti30Ni30 alloy membrane for hydrogen separation applications

Abstract

Our newly developed Nb35Mo5Ti30Ni30 alloy has been amended and evaluated for hydrogen separation applications in several critical aspects. Firstly, the hydrogen absorption and diffusion energetics in the Nb-Mo system are theoretically studied by density function theory. It is found that the addition of Mo in Nb can reduce the charge acquired by hydrogen and weaken the binding strength between the bcc-Nb lattice and hydrogen, thereby reducing hydrogen solubility. Additionally, optimized minimum energy paths for hydrogen diffusion are generated. These effects clarify the prominent role of Mo in the enhancement of both hydrogen permeability and embrittlement resistance. Secondly, as-cast Nb35Mo5Ti30Ni30 has been cold rolled to a thin membrane with a 0.12 mm thickness and then annealed. A hydrogen flux of ~ 0.21 mol H2 m−2s−1 is obtained for the rolled-annealed membrane at a pure H2 pressure difference of 0.7 MPa at 400 °C. Thirdly, the membrane is used to separate hydrogen from gas mixtures of H2/CO2 and H2/(CO2 + H2O). The hydrogen flux decreases mainly due to the decreasing H2 partial pressure. The membrane does not suffer any physical damage during the test, and the hydrogen flux is fully recovered afterwards.