Enhancement of hydrogen permeation stability at high temperatures for Pd/Nb₃₀Ti₃₅Co₃₅/Pd composite membranes by HfN intermediate layer

Composite membranes of Pd/Nb₃₀Ti₃₅Co₃₅/Pd exhibit high potential in hydrogen separation and purification applications. There are two factors, interlayer diffusion and aggregation of Pd, causing the flux degradation during long-term hydrogen permeation at high temperatures (>400 °C). HfN intermediate layer is used to restrict the interdiffusion between the Pd layer and the substrate layer. The long-term hydrogen permeation tests of Pd/HfN/Nb₃₀Ti₃₅Co₃₅/HfN/Pd composite membranes were conducted at temperatures from 500 to 600 °C. The HfN layer improved the permeation stability of the composite membranes in the temperature range of 500–550 °C. The enhanced effect of the HfN layer is related to the thickness of HfN and the operating temperature. A prediction model was proposed to reveal the flux-time dependence relationship with the influence of the HfN layer.