The hydrogen permeability of Pd4S

► Direct measurements of the hydrogen permeability of Pd4S show that H2S degrades the performance of Pd membranes primarily by producing a Pd4S film with low intrinsic H atom permeability-about an order-of-magnitude lower than that of Pd. ► The Pd4S films allow H atom transport; they do not completely block the H2 flux across the membrane. ► In addition to causing formation of low-permeability Pd4S, H2S in the feed gas also lowers H2 flux directly, possibly by blocking H2 dissociation sites.