Matthew Camaratta

High-Performance Composite Bi2Ru2O7 – Bi1.6Er0.4O3 Cathodes for Intermediate-Temperature Solid Oxide Fuel Cells

Porous composite electrodes consisting of Bi 2 RU 2 O 7 (BRO7) and Er 0.4 Bi 16 O 3 (ESB20) were synthesized and characterized using impedance spectroscopy on symmetrical cells. Electrode performance was manipulated compositionally by varying the weight percent of each phase in the composite. Microstructural influences on electrode resistance were examined by varying starting particle sizes of BRO7 and ESB20 powders and using a combination of sedimentation to further reduce particle size and size distributions as well as ultrasonication to break up soft agglomerates. The effect of electrode thickness was also studied by applying successive coats of the electrode inks to the electrolyte substrates. In addition, application of a pure BRO7 current collector was found to dramatically improve performance. Using these optimization techniques, a minimum electrode area specific resistance of 0.03 Ω cm 2 was attained at 700°C.

Development of High Performance Ceria/Bismuth Oxide Bilayered Electrolyte SOFCs for Lower Temperature Operation

This study examines the development of lower temperature solid oxide fuel cells (SOFCs) and the incremental improvement in performance obtained from a wide range of techniques, from pressed anodes to tape-cast anodes, from gadolinia-doped ceria (GDC) single-layer electrolytes to erbium-stabilized bismuth oxide (ESB)/GDC bilayer, and from La 0.6 Sr 0.4 Co 0.2 Fe 0.8 O 3-δ -GDC composite cathodes to optimized Bi 2 Ru 2 O 7 -ESB composites. GDC single-layer electrolyte-based SOFCs were prepared from four different fabrications and exhibit maximum power densities ranging from 0.338 to 1.03 W/cm 2 at 650°C. At each fabrication stage, an ESB layer was applied to form a bilayer electrolyte. ESB was deposited by a range of techniques including colloidal deposition and pulsed laser deposition. The result confirms that depending on a fabrication route, the bilayer electrolyte can reduce the total area specific resistance (ASR) 33-49% and increase the maximum power density 44-93%. By using a combination of the materials and fabrication routes, a maximum power density of 1.95 W/cm 2 and 0.079 Ω cm 2 total cell ASR was achieved at 650°C for a bilayer cell.

Enhanced oxygen reduction reaction with nano-scale pyrochlore bismuth ruthenate via cost-effective wet-chemical synthesis

Pyrochlore ruthenate oxides are promising electrocatalytic materials for lower temperature solid oxide fuel cell (LT-SOFC) cathodes due to their high catalytic activity toward oxygen reduction reaction (ORR) which is the major rate-limiting step at reduced temperatures (below 750 °C). Here we report for the first time highly pure pyrochlore bismuth ruthenate (Bi2Ru2O7, BRO7) synthesized via a practical and cost-effective glycine–nitrate (GNC) combustion method. The synthesis parameters including glycine to nitrate ratio and calcination conditions were systematically optimized, resulting in nanoparticles with crystallite size of ∼30 nm and significant reduction in synthesis steps. Incorporating the synthesized BRO7 nanoparticles with highly conductive bismuth oxide as an SOFC cathode results in significant enhancement of ORR, showing 9 times lower SOFC cathode area specific resistance, compared to that of BRO7 via conventional solid-state reaction. Thus, this result demonstrates the feasibility of BRO7 nanoparticles via GNC to enhance the ORR for lower temperature SOFC applications.