Influence of Oxygen Surface Exchanges on OxygenSemi-Permeation through La(1−x)SrxFe(1−y)GayO3−δDense Membrane

Abstract

Because of high oxygen semi-permeation and very good chemical stability, La 0.8 Sr 0.2 Fe 0.7 Ga 0.3 O 3Àd perovskite is one of the most promising materials as a catalytic membrane reactor for hydrogen production. In this paper, oxygen semi-permeation of La 0.8 Sr 0.2 Fe 0.7 Ga 0.3 O 3Àd membranes with different architectures is studied over a large range of temperatures in order to identify the rate determining step of the oxygen flux through the membrane. We show that the oxygen flux through the membrane is governed by the surface exchanges on the membrane reducing face. Besides, these results are confirmed by potentiometric measurements of oxygen activity on both membrane faces under oxygen partial pressure gradient. Finally, new architectures with La 0.8 Sr 0.2 Fe 0.7 Ni 0.3 O 3Àd porous catalytic layer on membrane reducing surface are tested to improve the performances of oxygen semi-permeation.

Evaluating oxygen diffusion, surface exchange and oxygen semi-permeation in Ln2NiO4+δ membranes (Ln=La, Pr and Nd)

“…The oxygen semi-permeation and the oxygen activities at the membrane surfaces were measured thanks to a specific setup presented in Error! Reference source not found.3 and described, with more details in a previous work [18]. A dense membrane of 1mm thick and 24 mm diameter was sealed between two alumina tubes using gold rings to obtain a tight system.…”

“…In previous works [18][19][20], the oxygen transport through oxide membranes has been decomposed into three main steps: 1) surface exchange on the oxygen-rich face, 2) oxygen diffusion through the membrane, and 3) surface exchange on the oxygen-lean face (Fig. 4).…”

“…The Wagner's model being typically applied to describe the oxygen flux through a membrane bulk [18], hence, one can determine the oxygen diffusion coefficient using (eq. 6)…”

Identification of the rate-determining step in oxygen transport through La(1−x)SrxFe(1−y)GayO3−δ perovskite membranes

“…3), described in previous studies [10,11]. The oxygenpermeation measurement was performed on two membrane samples for each membrane material to ensure reproducibility.…”

“…The determination of the oxygen chemical potential drop makes it possible to calculate a new criterion introduced in previous work [11], B c , which is defined in the following equation:…”