Hydrogen separation is an important step for the utilization of hydrogen energy. Metallic alloys, such as vanadium–nickel, are potential hydrogen separation materials. Due to the strong propensity of vanadium to form oxides and hydrides, vanadium alloy has a lower hydrogen permeability, and it is difficult to maintain the permeability over time. Therefore, special preparation processes such as Pd coating have been suggested for hydrogen separation vanadium-based membranes. However, aside from the prohibitive price of palladium, the interdiffusion of palladium and vanadium makes the coated membrane inviable to be used at a high temperature. Thermal treatment with inert gas was investigated in this study to assess the applicability of the vanadium alloy without palladium coating for hydrogen separation and clarify the mechanism behind the thermal treatment. Argon is inert with vanadium and displayed …