Effect of TiN/Pd catalytic layer on structure and hydrogen permeability of V92Fe4Pd4 hydrogen separation alloy

Traditional commercial Pd hydrogen separation alloy membranes have long suffered from scarcity and high costs, highlighting the urgent need for innovative hydrogen separation alternatives. V-based alloy membranes, on the other hand, exhibit higher hydrogen permeability and come at a lower cost compared to Pd alloy membranes, thus showing promising potential for hydrogen separation and purification applications. Herein, the ternary V₉₂Fe₄Pd₄ alloy substrate was prepared via arc melting, and TiN/V₉₂Fe₄Pd₄/TiN and Pd/V₉₂Fe₄Pd₄/Pd hydrogen separation membranes with 200 nm-thick catalytic layers were fabricated using magnetron sputtering. The results reveal that the TiN and Pd catalytic layers have uniform film formation, smooth surfaces, and integral structures. Under constant temperature and lower pressure conditions, the hydrogen permeation flux of both membranes has a linear relationship with the square root difference between the upper and lower pressures of the membrane. Notably, the hydrogen permeability coefficient of the TiN/V₉₂Fe₄Pd₄/TiN membrane increases with temperature, reaching 6.31 × 10⁻⁸ mol H₂ m⁻¹ s⁻¹ Pa^−0.5 at 673 K—higher than that of the Pd/V₉₂Fe₄Pd₄/Pd membrane (5.80 × 10⁻⁸ mol H₂ m⁻¹ s⁻¹ Pa^−0.5 under the same conditions). After a 70-h durability test at 673 K, TiN-coated V₉₂Fe₄Pd₄ retains ~ 78.9% of initial flux and Pd-coated ~ 79.8%, far outperforming the uncoated substrate (53.1% flux loss). Notably, the results suggest that the structural breakage of the TiN membrane surface in the TiN/V₉₂Fe₄Pd₄/TiN alloy membrane may be the contributing factor to the decrease in hydrogen flux.

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