Transport number measurements and fuel cell testing of undoped and Mo-substituted lanthanum tungstate

• Published in: Journal of power sources 2013-10, Vol.240, p.583-588
• Main Author: MAGRASO, Anna
• Format: Article
• Language: English
• Subjects: Applied sciences; Direct energy conversion and energy accumulation; Electrical engineering. Electrical power engineering; Electrical power engineering; Electrochemical conversion: primary and secondary batteries, fuel cells; Energy; Energy. Thermal use of fuels; Equipments for energy generation and conversion: thermal, electrical, mechanical energy, etc; Exact sciences and technology; Fuel cells; H2 permeable membrane; La28−xW4+xO54+δ; La6WO12; Mixed electron–proton conductor; PC-SOFC; Proton conductor
• ISSN: 0378-7753; 1873-2755
• DOI: 10.1016/j.jpowsour.2013.04.087

The partial protonic, oxide ion and electronic conductivities of lanthanum tungstate (La28−xW4+xO54+δ with x = 1, LWO54) and 30% molybdenum substituted lanthanum tungstate (Mo-LWO54) have been extracted using the EMF method. LWO54 is a relatively pure ionic conductor up to ∼800 °C; above that temperature electrons start to contribute significantly (under reducing conditions). The maximum protonic conductivity is ∼2–3 × 10−3 S cm−1, and protonic conductivity dominates the ionic regime under wet conditions below ∼700 °C. Above this temperature, oxide ion conductivity dominates the ionic contribution. The protonic and oxide ion conductivities for Mo-substituted LWO54 are quite similar to the Mo-free material, while the electronic conductivity is almost one order of magnitude higher for the former in wet 5% H2/Ar. From this report is clear that nominally undoped lanthanum tungstate is most suited for applications as electrolyte in proton conducting SOFCs, while Mo-LWO54 presents improved mixed proton-electron conductivity for use as dense membrane for hydrogen separation. •Partial conductivities have been extracted for LWO and Mo-LWO.•Lanthanum tungstate is suitable as electrolyte for PC-SOFCs.•Mo-substituted LWO is more suited as membrane material for H2 gas separation.