Ultrasound assistance in the sensitization and activation of porous Al2O3 supports for improving the hydrogen separation of Pd/Al2O3 composite membranes

Abstract

Pd membrane on porous Al2O3, an important composite membrane for H2 separation, is typically fabricated by electroless plating, and thus the quality of the Pd membrane is critically dependent on the seeding process. Here, a facile ultrasonication-assisted sensitization-activation process is used to load catalytic particles on porous Al2O3, subsequently followed by electroless plating of 5-μm-thick Pd membranes for H2 separation. Uniformly distributed catalytic particles with even sizes are loaded onto Al2O3 only under an optimal power of the ultrasonic agitation, then catalyzing electroless Pd membranes with a better surface topography and less defective microstructure. The optimal Pd membrane achieves a sound hydrogen flux of 0.157 mol m−2 s−1 and high H2/N2 selectivity of 1835 under 723 K and 105 kPa pressure difference. Moreover, this particular Pd/Al2O3 exhibits high stability in (a) Pd membrane microstructures and (b) H2/N2 permeating fluxes without elemental interfacial diffusion even under long-term (156 h) at a high temperature (723 K).