(701e) Electroless Plating of Palladium Onto a Cordierite Monolith for Portable Hydrogen Extraction

Integrated ceramic minichannel and microchannel membrane
networks comprised of cordierite monoliths packaged with appropriate fluid
distribution are being developed for hydrogen extraction from hydrocarbons. The
final membrane design is envisioned as a catalytic steam reforming layer; over
top a hydrogen-permselective palladium layer. By combining these technologies
it is expected to produce ultra pure hydrogen in a single integrated device for
portable power systems application¹. In this talk, we present
progress to-date in coating thin permselective palladium films within the cordierite
minichannel network for hydrogen purification.

In this study, palladium films have been deposited by
electroless plating on top of an alumina supporting layer, itself deposited
within a cordierite matrix. The alumina supporting layer was coated inside the
cordierite channels by wash-coating method to achieve a smooth, uniform coat. 
This was accomplished in two steps, first laying down a micro-sized layer of γ-alumina
to achieve a low-stress deposition surface, followed by deposition of a
nano-sized γ-alumina layer to produce a smooth, crack-free, and pinhole-free
alumina layer that is ideal for plating Palladium. Two electroless plating
methods were compared for depositing thin Palladium films on the resulting
substrate. Each palladium film was tested for permeability and permselectivity
by flowing hydrogen / helium mixtures through the channels at 350°C. 
  

In this talk we will present details on the coating methods
used to prepare the cordierite substrate, plating techniques for realizing
permselective membranes, and packaging strategies to ensure stable, leak-free
operation. With this there will be a general discussion of how these different
variables factor into the selectivity and permeability of the resulting membrane. 
SEM imaging and EDS analysis were used to examine the thin film morphology.
Leak testing and selectivity testing were used to examine the overall
performance of the palladium films.  To-date, films have been developed that
achieve a hydrogen permeation rate of 0.004-0.017moles/m²s, and hydrogen-to-helium
selectivities of  40-100.

¹ B.A. Wilhite, S.E.
Weiss, J.Y. Ying, M.A. Schmidt and K.F. Jensen, "Demonstration of 23wt%
Ag-Pd Micromembrane Employing 8:1 LaNi_0.95Co_0.05O₃/Al₂O₃
Catalyst for High-Purity Hydrogen Generation," Advanced Materials, 18,
1701 (2006).