The enhanced electrochemical response of Sr(Ti 0.3 Fe 0.7 Ru 0.07 )O 3−δ anodes due to exsolved Ru–Fe nanoparticles

GLASER, R.; ZHU, T.; TROIANI, H.; CANEIRO, A.; MOGNI, L.; BARNETT, S.

Journal of Materials Chemistry A

The Royal Society of Chemistry

Año: 2018 vol. 6 p. 5193 - 5201

2050-7488

Mixed conducting oxide with nominal composition Sr(Ti0.3Fe0.7Ru0.07)O3-? (STFRu) is studied, in comparison with SrTi0.3Fe0.7O3-? (STF) oxide, as anodes for solid oxide fuel cells. Exposing STFRu to reducing fuel conditions at 800 ??C for 4 h results in theexsolution of essentially all of the Ru and a small fraction of the Fe from the oxide, and the formation of Ru1-xFex nanoparticleson the oxide surfaces. Most of the nanoparticles have the hexagonal structure expected for Ru-rich alloys, andthermogravimetric analysis suggests the composition x ~ 0.2. A small fraction of bcc-structure, presumably Fe-rich,nanoparticles are also detected. Comparison of cells with STFRu and STF anodes shows that the presence of Ru induces areduced polarization resistance and increase the maximum power density for most cell operating conditions, particularly atlower temperatures and hydrogen partial pressures. For example, at 700 ??C and 30% H2 fuel, the maximum power densityis 0.1 W/cm2 for STF compared to 0.3 W/cm2 for STFRu. There is also a significant change in the shape of the current-voltagecurves and the 𝑝𝐻2-dependence of the anode polarization resistances 𝑅𝑃,𝐴 ?å (𝑝𝐻2 )−𝑚, from m ~ 0.5-1.0 for STF to m ~ 0.11-0.29 for STFRu; these suggest that Ru1-xFex nanoparticles improve anode performance by promoting hydrogen adsorption.