Oxygen transport kinetics of MIEC membranes coated with different catalysts

Abstract

in Wiley Online Library (wileyonlinelibrary.com)Oxygen permeation through mixed ionic-electronic conducting membrane may be controlled by oxygen bulk diffusion and/ or oxygen interfacial exchange kinetics. In this article, we chose BaCe 0.05 Fe 0.95 O 3-d (BCF) as a representative to study the oxygen transport resistances of the membrane coated with different porous catalysts, including BCF itself, Ba 0.5 Sr 0.5 Co 0.8-Fe 0.2 O 3-d (BSCF) and Sm 0.5 Sr 0.5 CoO 3-d (SSC). The oxygen transport resistances of bulk, gas-solid interfaces of feed-side and sweep-side of the catalyst-coated membranes can be separately obtained through a linear regression of experimental data according to an oxygen permeation model. The three resistances of the membrane coated with BCF catalyst are smaller than those of the membrane coated with BSCF and SSC catalysts, although BSCF catalyst itself has the fastest bulk diffusion and interfacial exchange kinetics. The catalytic activities of BSCF and SSC catalysts on BCF membranes are impacted by the transport kinetics of catalysts, microstructure of catalyst layers, and cationic inter-diffusion between the membrane and catalysts.

Selection of oxygen permeation models for different mixed ionic‐electronic conducting membranes

“…The parameters obtained through fitting are listed in Table 5, they are all similar to our previous work. 37 As shown in Figure 6b, when the same group of data are fitted to Xu-Thomson's 55,56 Studies on La 1-x Sr x CoO 3-d disclosed that the oxygen nonstoichiometry was a function of temperature, Sr content, and equilibrium oxygen partial pressure. When x 5 0.3, the oxygen nonstoichiometry of La 0.7 Sr 0.3 CoO 3-d (LSC) changes obviously with the change of oxygen partial pressure at elevated temperatures, 57 as shown in Figure 5.…”

“…The process of oxygen permeation is complicated, including many steps, such as gaseous mass transfer to/from the gas–solid interface, oxygen exchange on the gas–solid interfaces of both feed side and permeate side, respectively, and bulk diffusion of both oxygen ions/vacancies and electrons/holes. Several permeation models were proposed by different groups to illustrate the oxygen permeation mechanism through MIEC membranes . Wagner theory is the earliest one to be used to describe the oxygen permeation process by assuming the bulk diffusion to be the rate‐determining step (r.d.s).…”

“…Several permeation models were proposed by different groups to illustrate the oxygen permeation mechanism through MIEC membranes. 32,33,[35][36][37] Wagner theory is the earliest one to be used to describe the oxygen permeation process by assuming the bulk diffusion to be the rate-determining step (r.d.s). However, subsequent investigations revealed that the oxygen exchange reactions on both gas-solid interfaces must be taken into account as the membrane thickness decreases to a certain value.…”

“…Recently, Zhu et al 28 developed an explicit oxygen permeation model based on a theoretical analysis of the electrochemical process of oxygen permeation through an MIEC membrane, and they successfully applied this model to BSCF and other MIEC membranes. 6,23,28,36,37 In this article, we call this model as Zhu's model for a brief expression.…”

Microstructural and Interfacial Designs of Oxygen‐Permeable Membranes for Oxygen Separation and Reaction–Separation Coupling

“…With the help of theoretic model studies, the microstructural and interfacial effects can be well described . With the advanced strategies, the stability and permeability of membranes can be improved simultaneously . In this work, we describe the recent efforts to build models to aid in the understanding of the important effects of the surface and grain boundaries on the stability of the membranes, design novel MIEC membrane materials for oxygen transport and catalytic reactions, and utilize the developed membranes to construct membrane reactors for new separation and reaction processes with high efficiencies.…”