A CO2-Stable K2NiF4-Type Oxide (Nd0.9La0.1)2(Ni0.74Cu0.21Al0.05)O4+δ for Oxygen Separation

Transition metal oxide-based membranes for oxygen separation

Tonnage oxygen production is still mostly based on the traditional technology of cryogenic distillation, a century-old, capital- and energy-intensive method. It is critical to create a novel low-cost, energy-efficient approach that can meet the growing demand for oxygen in industry from the clean environmental or energy standpoint. Ruddlesden-Popper (RP) perovskite like oxides -based ionic transport membranes for the oxygen transport have recently been developed as a possible replacement for the traditional cryogenic approach. In this work, we detailly reviewed the progress of RP perovskite oxides based membranes for oxygen transport from separation mechanism, material types, synthesis methods to the final separation performance. This work advances the development of RP perovskite membranes for oxygen transport.

Rational design of mixed ionic-electronic conducting membranes for oxygen transport

The mixed ionic-electronic conducting (MIEC) oxides have generated significant research efforts in the scientific community during the last 40 years. Since then, many MIEC compounds, most of which are based on perovskite oxides, have been synthesized and characterized. These compounds, when heated to high temperatures, form solid ceramic membranes with high oxygen ionic and electrical conductivity. The driving force for oxygen ion transport is the ionic transfer of oxygen from the air as a result of the differential partial pressure of oxygen across the membrane. Electronic and ionic transport in a range of MIEC materials has been studied using the defect theory, particularly when dopants are introduced to the compound of interest. As a result, many types of ionic oxygen transport limits exist, each with a distinct phase shift depending on the temperature and partial pressure of oxygen in use. In combination with theoretical principles, this work attempts to evaluate the research community's major and meaningful achievements in this subject throughout the preceding four decades.

Designing CO2-resistant oxygen-selective mixed ionic-electronic conducting membranes: guidelines, recent advances, and forward directions

CO₂ resistance is an enabling property for the wide-scale implementation of oxygen-selective mixed ionic-electronic conducting (MIEC) membranes in clean energy technologies, i.e., oxyfuel combustion, clean coal energy delivery, and catalytic membrane reactors for greener chemical synthesis. The significant rise in the number of studies over the past decade and the major progress in CO₂-resistant MIEC materials warrant systematic guidelines on this topic. To this end, this review features the pertaining aspects in addition to the recent status and advances of the two most promising membrane materials, perovskite and fluorite-based dual-phase materials. We explain how to quantify and design CO₂ resistant membranes using the Lewis acid-base reaction concept and thermodynamics perspective and highlight the relevant characterization techniques. For perovskite materials, a trade-off generally exists between CO₂ resistance and O₂ permeability. Fluorite materials, despite their inherent CO₂ resistance, typically have low O₂ permeability but this can be improved via different approaches including thin film technology and the recently developed minimum internal electronic short-circuit second phase and external electronic short-circuit decoration. We then elaborate the two main future directions that are centralized around the development of new oxide compositions capable of featuring simultaneously high CO₂ resistance and O₂ permeability and the exploitation of phase reactions to create a new conductive phase along the grain boundaries of dual-phase materials. The final part of the review discusses various complimentary characterization techniques and the relevant studies that can provide insights into the degradation mechanism of oxide-based materials upon exposure to CO₂.