Hebb-Wagner polarization assessment of enhanced oxygen permeability for surface modified oxygen transport membranes. (20th July 2017) - Liu, Xuejiao
Abstract: Tri-layered "porous | dense | porous" La0.8 Sr0.2 Cr0.5 Fe0.5 O3−δ -Zr0.84 Y0.16 O2−δ (LSCrF-YSZ) oxygen transport membranes (OTMs) were fabricated and permeation resistances from oxygen reduction and evolution reactions were determined by using Hebb-Wagner polarization method after introducing additional electron-blocking YSZ thin layers within the dense LSCrF-YSZ layers. Adding nano-scale catalysts, i.e. La0.6 Sr0.4 Co0.2 Fe0.8 O3−δ (LSCoF) on air side and Ce0.8 Sm0.2 O1.9−δ /Ni (SDC/Ni) on CH4 side, into the porous LSCrF-YSZ layers yielded substantially reduced interfacial polarization resistances, and thereby allowed for high oxygen permeability at reduced temperatures under the air/CH4 gradient, e.g ., 1.1 and 4.3 ml cm −2 min −1 at 650 and 800 °C, respectively. Analysis of the impedance spectra suggest that the oxygen reduction kinetics on air side was probably limited by charge transfer reaction at T ≥ 750 °C and surface oxygen exchange at T ≤ 700 °C. Meanwhile, oxygen evolution reactions on CH4 side dominated the total resistances to oxygen permeation through the tri-layered OTMs. Highlights: Tri-layered "porous | dense | porous" La0.8 Sr0.2 Cr0.5 Fe0.5 O3−δ -Zr0.84 Y0.16 O2−δ oxygen transport membranes were fabricated. La0.6 Sr0.4 Co0.2 Fe0.8 O3−δ and Ce0.8 Sm0.2 O1.9−δ /Ni nano-scale catalysts on porous layers were developed. Oxygen evolution reactions dominated the total resistances to oxygen permeation. 4.3 ml cm −2 min −1 oxygen permeability was yield at 800 °C under the air/CH4 gradient.