Composite electrolyte membranes for high temperature CO₂ separation

A membrane device that can selectively separate CO₂ at temperatures exceeding 600°C has been demonstrated. The membrane can be made from a composite material made of a molten carbonate electrolyte that fills the pore space in a solid oxide electrolyte (e.g. yttria doped zirconia (YSZ), or gadolinia doped ceria (CGO)). The experimental evidence points to a transport mechanism based on opposing ionic currents of carbonate and oxide ions. The flux of CO₂ across these membranes has been shown to increase with temperature, reaching permeabilities of 10^-11molm^-1s^-1Pa^-1 (or permeance of 3×10^-8molm^-2s^-1Pa^-1) at 850°C. The use of a non-ion conducting solid oxide, Al₂O₃, does not result in strong CO₂ permeability or selectivity, supporting a facilitated dual-ion transport mechanism.