Enhancing hydrogen separation efficiency: Insights from the permeability study of nickel-based composite membranes

Abstract

This research aims to validate the capability of composite nickel-based membranes in separating hydrogen and to examine how multi-layer deposits influence the density of the nickel film. The study evaluated the hydrogen permselectivity of the membranes for both single gases (H2, N2) and binary mixtures over a temperature range from 25 °C to 700 °C. The findings revealed that the thickness of the nickel layer (ranging from 2 μm to 37 μm) and its adhesion to the support material affected the hydrogen transport through the films. Increasing the number of electroless plating treatments and the nickel thickness on γ-alumina and α-alumina tubular supports resulted in decreased hydrogen permeance but improved hydrogen selectivity. This was attributed to the enhanced recovery of the γ-alumina support and efficient filling of α-alumina support pores, depending on the membrane type. The study identified multiple mechanisms contributing to hydrogen transport, including surface diffusion, Knudsen diffusion at lower temperatures (<300 °C), and activated diffusion processes at higher temperatures (>300 °C). At 700 °C, for a Ni/0.8 μm-α-Al2O3 membrane with a 37 μm nickel film, the hydrogen permeance for single gases was 5.8 × 10−8 mol/m2 s Pa (189 GPU: gas permeance unit) with an ideal selectivity of 199 towards N2. It was 7.3 × 10−8 mol/m2 s Pa (238 GPU) for gas mixtures with an H2/N2 separation factor of 148. These results suggest that these membranes are particularly effective at high temperatures, emphasizing their potential for hydrogen separation applications and positioning them as promising materials for further development in this field.