V-Cr-Cu dual-phase alloy membranes for hydrogen separation: An excellent combination of ductility, hydrogen permeability and embrittlement resistance

V-Cr-Cu alloys consisting of bcc-(V) and fcc-(Cu) are developed as a new type of hydrogen permeable metal membranes based on the idea of distributing functions on the different phases. The bcc-(V) is mainly responsible for hydrogen permeation, and the fcc-(Cu) imparts improvement in ductility. The addition of Cr in as-cast (V_100−xCr_x)₇₀Cu₃₀ (x=0…10 at%) alloys reduces the hydrogen solubility and thus improves the hydrogen embrittlement resistance, but decreases the hydrogen diffusivity and permeability. As-cast (V₉₅Cr₅)₇₀Cu₃₀ exhibits an excellent combination of ductility, hydrogen permeability and embrittlement resistance. After cold rolled to a thin foil of ~100 µm in thickness and subsequent annealing, this alloy membrane shows a pronounced high hydrogen permeation flux, particularly ~34 cc H₂ cm⁻²min⁻¹ at a hydrogen pressure difference of 0.7 MPa at 673 K. This corresponds to a permeability of ~3.98×10⁻⁸ mol H₂ m⁻¹s⁻¹Pa^−0.5. This work demonstrates that the dual-phase structure in V-Cr-Cu alloys ensures a feasible route for a large scale fabrication of thin membranes by cold rolling that features high hydrogen permeation proprieties.