Current developments of mixed conducting membranes on porous substrates

Abstract

The fabrication of mixed ionic-electronic conducting (MIEC) ceramic-based membranes for oxygen separation has extensively increased in the last three decades as a promising alternative of clean energy delivery. In recent years, the interest on supported MIEC membranes has increased due to their attractive properties such as higher mechanical strength and oxygen flux compared to selfsupported membranes. This work presents a literature review on the development of supported MIEC membranes of perovskite structure. The concepts and transport mechanism of those membranes are explained and recent works on supported MIEC membranes are presented. Finally, manufacturing methods of self-supported membranes and their influence on oxygen permeation are discussed.

Review of perovskite ceramic synthesis and membrane preparation methods

“…These challenges will have to be preceded by novel perovskite material synthesis with proven capability, high oxygen ionic conduction and stability for long term operation. [15]. Fig.…”

“…However, there are five steps associated with oxygen transport which are worth mentioning as follows (Fig. 2) [15]:…”

Development of Robust Mixed‐Conducting Membranes with High Permeability and Stability

“…Literally almost 90 % of the periodic table can form perovskite compounds with ideal compositional formula of A 2+ B 4+ O 3 being the compositions A 1+ B 5+ O 3 and A 3+ B 3+ O 3 also possible if the total charge of the A and B cations equals that of oxygen [1,2]. The A-site cation can be a rare earth, alkali or alkaline earth ion, such as La, Na, Ca, Sr or Ba, while the B-site is a transition metal, such as Ti, Zr, Fe, Co, Ni or Cu [3,4].…”

“…In these mixed conductors, the ionic conductivity takes place in these materials by the so-called hopping mechanism in which oxide ions move from oxygen vacancy to oxygen vacancy, besides this, electronic conduction occurs through B n+ -O-B (n+1)+ pairs formed to assure the overall electroneutrality of the material. Therefore, materials of A x A' 1-x B y B' 1-y O 3-δ composition results in mixed conductors whose conductivity depends on the nature of the doping cations [1,2]. The defect chemistry of perovskites marks their application.…”

Shaping of 3YSZ porous substrates for oxygen separation membranes

“…The requirements of the porous support respect to the MIEC layer are that they should present chemical compatibility, similar thermal expansion coefficient, good gas permeation and excellent mechanical properties under operation conditions [16]. In this sense, 3 mol% Yttria stabilized Zirconium (3YSZ) meets the requirements as substrate, due to it high chemical stability and high mechanical properties.…”