Effect of molten carbonate composition on CO2 permeation mechanism

High temperature dual-phase mixed conductor membranes are promising for CO 2 separation and utilization. Most efforts are focused on materials, thickness, microstructural features and surface modifications of the electronic conducting phase. Here, we unveil the effect of the carbonate-ionic conducting phase on CO 2 permeation process with a dense NiO-based dual-phase membrane. The results demonstrate that the CO 2 flux increases first and then decreases with the increase of Li 2 CO 3 addition amount. The controlling step of CO 2 permeation changes from bulk diffusion to surface reaction as much more Li 2 CO 3 was added into the carbonate-ionic conducting phase. Model analysis indicates that the peroxide formation process on the membrane surface is the rate-limiting step, which is closely related to the oxygen solubility of molten carbonate.