Thin Pd membrane on a modified porous stainless steel tube: Al2O3 particle size selection strategy

Abstract

Palladium (Pd) membranes for hydrogen separation were deposited on modified porous stainless steel (PSS) tubes using the electroless plating technique. This study explores the hydrogen permeance influenced by the effect of reducing the thickness of the Pd membrane using different sizes of Al2O3 particles, 10 and 1 µm, to modify the pores on the PSS surface. The pore size on the surface of the PSS tubes modified with 10 µm Al2O3 particles decreased from 10 ∼ 20 µm to less than 5 µm, while the surface of the PSS, modified by 1 µm Al2O3, was very dense and smooth. Generally, the supporting tubes with smaller pore size on the surface give thinner Pd membrane. The minimum thickness of a dense Pd membrane decreased from 35.1 to 16.2 µm when using 1 µm Al2O3 particles to modify the PSS tubes, but the maximum hydrogen permeance was enhanced from 15.3 to 34.7 m3/m2 h atm0.5 at 500°C by using 10 µm Al2O3 particles. This evidence demonstrated the hydrogen permeance has a trade-off between the porosity (effective passages) and thickness of the Pd membranes since both are influenced by the Al2O3 particle size used in the surface modification. These results suggested a promising and simple approach to produce a Pd membrane with high hydrogen permeance.