International Journal of Hydrogen Energy, Vol.42, No.29, 18410-18416, 2017
Hebb-Wagner polarization assessment of enhanced oxygen permeability for surface modified oxygen transport membranes
Tri-layered "porous I dense I porous" La0.8Sr0.2Cr0.5Fe0.5O3-delta-Zr0.84Y0.16O2-delta (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. La0.6Sr0.4CO0.2Fe0.8O3-delta (LSCoF) on air side and Ce0.8Sm0.20O1.9-delta/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 degrees 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 degrees C and surface oxygen exchange at T <= 700 degrees C. Meanwhile, oxygen evolution reactions on CH4 side dominated the total resistances to oxygen permeation through the tri-layered OTMs. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.
Keywords:Oxygen transport membranes;Oxygen permeability;Surface modification;Nanostructures;Catalysts