Enhanced hydrogen permeability and reverse water-gas shift reaction activity via magneli Ti4O7 doping into SrCe0.9Y0.1O3-δ hollow fiber membrane

Hydrogen proton conducting perovskite-based hollow fiber membrane is an attractive hydrogen separation technology that shows higher stability relative to Pd-based membranes above 800 degrees C. One of the challenges towards high hydrogen (H-2) permeability on such proton conducting membrane is enabling simultaneously high proton and electronic conductivities to be achieved in single phase membrane. This has been addressed by developing dual-phase membrane. Here, we showed another promising approach, i.e., exploitation of beneficial phase reactions to create new conductive phases along the grain boundaries. By doping up to 8 wt. % magneli Ti4O7 into SrCe09Y0.1O3-delta (SCY), Ce-doped SrTiO3 and Y-doped CeO2 were created in-between SCY grains. Electrical conductivity tests confirmed higher conductivities for 5 and 8 wt. % Ti4O7-doped SCY relative to SCY between 750 and 950 degrees C. These higher conductivities manifested into higher H-2 permeation fluxes for the doped SCY membranes. The highest flux of 0.17 mL min(-1)cm(-2) was observed for 5 wt. % Ti4O7-doped SCY at 900 degrees C when 50 vol. % H-2/He and 100 vol. % N-2 were used in the feed side and the permeate side, respectively. This is much higher than the flux of 0.05 mL min(-1) cm(-2) obtained from SrCe0.9Y0.1O3 membrane at identical condition. More essential is the fact that the doped SCY membranes displayed catalytic activity for the reverse water-gas shift (RWGS) reaction which consumed H-2 in the permeate side; increasing the H-2 flux up to 0.57 mL min(-1)cm(-2) at 900 degrees C. The 5 wt. % Ti407-doped SCY furthermore showed stable flux for more than 140 h at 850 degrees C despite the formation of minor amount of SrCO3 in H-2-CO2-containing atmosphere; highlighting its potential application as membrane reactor for RWGS or dehydrogenation reaction. (C) 2017 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.