1. Introduction
Development of compact hydrogen separators is of key
importance in hydrogen energy utilization, and intensive
attention has been paid to hydrogen-permeable membranes,
among which palladium membranes have been commercially
applied in hydrogen purification for about 50 years. They are
usually fabricated by multi-step cold-rolling and annealing,
and the membrane thickness can be up to 100 mm [1e4]. To
reduce the membrane thickness for higher hydrogen per-
meance and lower noble metal consumption, a composite
membrane concept has been introduced, which is comprised
of a thin layer of palladium or palladium alloy