Innovative MIEC-Redox Oxygen Separation Membranes with Combined Diffusion-Bubbling Mass Transfer: A Brief Review

Abstract

Oxygen plays a crucial role both in human life and in human economic activity and is the third (by volume) product in the world. Accelerated development of advanced energy technologies (solar photovoltaic and petrochemical industries) as well as biotechnology has stimulated the demand for ultra-high purity oxygen (above 99.999% purity). A newly developed copper and vanadium oxidebased two-layer mixed ionic electronic conducting -redox (MIEC-Redox) membrane with combined diffusion-bubbling oxygen mass transfer is of technological interest for ultra-high purity oxygen production as it demonstrates excellent oxygen selectivity and is easily made of affordable and inexpensive materials. Fundamental understanding of the formation, microstructure, and transport properties of MIEC-Redox membranes is important to be able to synthesize them in a controlled way and assess their potential for technological exploitation. The present article highlights the latest progress made in developing this understanding and outlines the further research directions. The ways to enhance the efficiency of oxygen separation through using these innovative diffusion-bubbling membranes are discussed. The proposed strategy of transition metal oxides-based thick membrane materials with fast combined diffusion-bubbling oxygen mass transfer opens up new vista for the design of next-generation energy materials with enhanced oxygen transport.

A core‐shell structured diffusion‐bubbling membrane for efficient oxygen separation: Formation and transport properties

“…If $$R$$ < $${R_{cr}}$$, the bubble disappears and, vice versa, it grows at $$R$$ > $${R_{cr}}$$. The oxygen bubble growth in diffusion‐bubble membrane can be described within the framework of a diffusion model 23,24 . This model assumes the formation of a diffusion envelope with low concentration of oxygen around the bubble.…”

“…The oxygen bubble growth in diffusion-bubble membrane can be described within the framework of a diffusion model. 23,24 This model assumes the formation of a diffusion envelope with low concentration of oxygen around the bubble. In the envelope, new bubble nucleation is excluded.…”

Oxygen-Selective Diffusion-Bubbling Membranes with Core–Shell Structure: Bubble Dynamics and Unsteady Effects

“…An oxygen electrochemical potential gradient across the membrane drives oxygen permeation. Reproduced/adapted with permission from ref . Copyright 2019 IOP.…”

“…Recently, diffusion-bubbling molten oxide membrane-based oxygen separation technology has been developed . New diffusion-bubbling membranes with core–shell structure (Figure a) and combined oxygen mass transfer show promise for efficient oxygen separation. , In such membranes, both the mixed-conducting shell and bubble-transporting core are composed of molten and solid phases. Under a gradient of chemical potential of oxygen, the volume fraction and composition of the molten phase in the membrane shell and core are different (10–15% and 45–50% molten phase volume fraction in the shell and core, respectively).…”

“…Ambipolar diffusion of oxygen ions in the membrane shell is the slowest of these three and limits the oxygen permeation rate. Oxygen flux ( j O 2 ′ ) through the membrane shell is described by eq where φ m is the volume fraction of the molten phase in the membrane shell, D i is the diffusion coefficient of oxygen ions in the molten phase, L s is the membrane shell thickness, M and ρ m are the molar mass and density of the molten phase, respectively, P O 2 ′ and P O 2 ″ are the partial pressures of oxygen at the feed (air) and permeate membrane sides, respectively, and N = 1 or N > 1 for ionic or polymer melt, respectively. The estimated by eq oxygen permeation flux through the membrane shell with a thickness L s = 0.3 mm is 8.3 × 10 –8 mol cm –2 s –1 .…”