abstract
Oxide + salt composites can be used in CO2 and NOx separation membranes, where high oxide-ion conductivity is crucial to improve performance. Pursuing this goal, the stability of three different bismuth oxide-based electrolytes (Cu + V, Y and Yb-doped) against molten alkali carbonates (Li, Na, K) or nitrates (Na, K) was tested firing them in the 450-550 degrees C temperature range, and with endurance tests up to 100 h. A well-known ceriabased composite was used as reference (CGO - Ce0.9Gd0.1O1.95). Oxides and composites were studied by X-ray diffraction, scanning electron microscopy and impedance spectroscopy (in air, 140-650 degrees C temperature range). Bi2Cu0.10V0.90O5.35 easily reacts with molten salts. Bi0.75Y0.25O1.5 and Bi0.75Yb0.25O1.5 have higher stability against molten carbonates and complete stability against molten nitrates. The Y-doped oxide stability against the molten carbonates was enhanced changing the molten salt composition (Y2O3 additions) and using lower firing temperatures. Above all, composites based on Y or Yb-doped Bi2O3 with molten alkali nitrates showed impressive 6x or 3x higher electrical conductivity at 290 degrees C, in air (4.88 x 10(-2) and 2.41 x 10(-2) S cm(-1), respectively) than CGO-based composites (7.72 x 10(-3) S cm(-1)), qualifying as promising materials for NOx separation membranes.
keywords
TRANSPORT-PROPERTIES; MOLTEN CARBONATES; HIGH-TEMPERATURE; METAL-OXIDES; STABILITY; CONDUCTION; PHASE; MODEL; PERFORMANCE; SYSTEMS
subject category
Materials Science
authors
Starykevich, M; Jamale, A; Marques, FMB
our authors
Maksim Starykevich
Junior ResearcherProjects
acknowledgements
This work was funded by projects CO2ZERO (POCI-01-0145-FEDER-016654-PTDC/CTM-CER/6732/2014), MOCO3 - (M-ERA.NET2 2016 -MOCO3-0009/2016), and CICECO-Aveiro Institute of Materials, UIDB/50011/2020 & UIDP/50011/2020, financed by national funds through FCT (Fundacao para a Ciencia e a Tecnologia)/MCTES, and when applicable co-financed by FEDER under the COMPETE 2020 Program. Specific support (AJ) provided by national funds (OE), through FCT, IP, in the scope of the framework contract foreseen in the numbers 4, 5, and 6 of the article 23, of the Decree-Law 57/2016, of August 29, changed by Law 57/2017, of July 19.