Asymmetric tubular ceramic-ceramic (cercer) membranes based on La27W3.5Mo1.5O55.5-δ-La0.87Sr0.13CrO3-δ were fabricated by a two-step firing method making use of water-based extrusion and dip-coating. The performance of the membranes was characterized by measuring the hydrogen permeation flux and water splitting with dry and wet sweep gases, respectively. To explore the limiting factors for hydrogen and oxygen transport in the asymmetric membrane architecture, the effect of different gas flows and switching the feed and sweep sides of the membrane on the apparent hydrogen permeability was investigated. A dusty gas model was used to simulate the gas gradient inside the porous support, which was combined with Wagner diffusion calculations of the dense membrane layer to assess the overall transport across the asymmetric membrane. In addition, the stability of the membrane was investigated by means of flux measurements over a period of 400 h.
Keywords: asymmetric tubular membrane; hydrogen permeation; lanthanum chromite; lanthanum tungstate; surface kinetics; water splitting.