Effects of lanthanides on the structure and oxygen permeability of Ti-doped dual-phase membranes

The trade-off effect of the oxygen permeability and stability of oxygen transport membranes (OTMs) still exists in working atmospheres containing CO₂. Herein, we reported a new series of 60 wt%Ce_0.9Ln_0.1O_2-δ-40 wt%Ln_0.6Sr_0.4Fe_0.9Ti_0.1O_3-δ (CLnO-LnSFTO, Ln = La, Pr, Nd, Sm, Gd, Tb) dual-phase OTMs by selecting different Ln elements based on the reported highly stable Ti-doped CPrO-PrSFTO. The effects of different Ln elements on the structure and oxygen permeability of Ti-doped dual-phase OTMs were systematically studied. Basically, as the atomic number of Ln elements increases, the unit cell parameters of both the fluorite phase and the perovskite phase become smaller. The unit cell volume and spatial symmetry of the perovskite phase are reduced, resulting in a reduction in oxygen permeability. The optimal CLaO-LaSFTO showed $J_{O_2}$ of 0.60 and 0.54 mL min⁻¹ cm⁻² with He and CO₂ sweeping at 1000 °C, respectively. In addition, all CLnO-LnSFTO OTMs could work for more than 100 h with no significant performance degradation in a CO₂ atmosphere, maintaining excellent stability. This work explores candidate OTM materials for CO₂ capture and oxygen separation, as well as provides some ideas for addressing the trade-off effect.