Microsystem technology for high-flux hydrogen separation membranes

The application of thin hydrogen-selective membranes suffers from the occurrence of pinholes and a significant resistance to mass transfer in the porous support. To overcome these problems, Pd, Pd/Ag and Pd–Ta–Pd membranes with a thickness between 0.5 and 1.2 μm have been deposited on a dense and smooth surface of a silicon wafer. After membrane deposition, the underground has been etched to release the membrane surface for H2 permeation. Membranes have been prepared with a 1 μm thick microsieve as the support or without support. The prepared membranes have been characterized by the H2 and He flux as a function of temperature (623–723 K) and feed composition (0 < pH2 < 0.83 bar). The highest H2 flux, 3.6 mol H2/(m2 s), has been found with a microsieve-supported 1 μm thick Pd/Ag membrane at 723 K and 0.83 bar hydrogen partial pressure. The fluxes measured here are approximately one order of magnitude higher than the fluxes reported in the literature for Pd or Pd alloy membranes deposited on porous supports. Moreover, helium could not be detected in the permeate, thus indicating the absence of pinholes.