Hydrogen separation membranes annual report for FY 2009.

Hydrogen separation membranes annual report for FY 2008.

“…Due to the presence of H 2 S (see Table 1), the flux decreased slowly during test 2a, but it stabilized at a value only ≈10% lower than its initial value. We have reported similar behavior for Argonne's cermet membranes during their exposure to H 2 S concentrations that were not high enough to cause formation of Pd 4 S [4]. During test 2b, the flux also decreased ≈10% from its initial value and then appeared to reach a stable value.…”

“…Hydrogen sulfide (H 2 S) is a particularly corrosive contaminant that HTMs are expected to encounter. When H 2 S reacts with palladium, palladium sulfide (Pd 4 S) forms on the HTM's surface and impedes hydrogen permeation; therefore, the conditions for Pd 4 S-formation largely determine an ANL-3e membrane's tolerance for H 2 S. We determined the temperatures at which Pd 4 S forms in specific feed gases containing 10-73% H 2 and ≈8-400 ppm H 2 S [1] and located the Pd/Pd 4 S phase boundary at 500-600°C in feed gas with 10% H 2 [3,4]. We correlated phase boundary data and hydrogen flux data for Pd foils and ANL-3e disks by measuring hydrogen flux while increasing the H 2 S concentration in the feed gas.…”

Hydrogen production by water dissociation using ceramic membranes. Annual report for FY 2009.

“…This project grew from an effort to develop a dense ceramic membrane for separating hydrogen from gas mixtures such as those generated during coal gasification, methane partial oxidation, and water-gas shift reactions [1]. That effort led to the development of various cermet (i.e., ceramic/metal composite) membranes that enable hydrogen production by two methods.…”

“…In one method, a hydrogen transport membrane (HTM) selectively removes hydrogen from a gas mixture by transporting it through either a mixed protonic/electronic conductor or a hydrogen transport metal. In the other method, an oxygen transport membrane (OTM) generates hydrogen mixed with steam by removing oxygen that is generated through water splitting [1,2].…”

“…Others have used mixed-conducting OTMs to produce hydrogen by water dissociation, but the membranes had low electronic conductivity, and the hydrogen production rate was modest even at high temperature (e.g., 0.6 cm 3 (STP)/min-cm 2 at 1683°C [8]). We achieved a significantly higher hydrogen production rate using an OTM composed of an oxygen-ion conductor of cerium gadolinium oxide (CGO) and an electronic conductor (Ni) [2]. The hydrogen production rate increased with increases in temperature, water partial pressure on the hydrogen-production side of the membrane, and oxygen chemical potential gradient across the membrane [2].…”