Sota Shimizu

Evaluation of Micro LSM-Supported GDC/ScSZ Bilayer Electrolyte with LSM–GDC Activation Layer for Intermediate Temperature-SOFCs

A gadolinium-doped ceria (GDC)/scandia-stabilized zirconia (ScSZ) bilayer electrolyte on a microtubular (La, Sr) x MnO 3-δ (LSM) support was prepared via extrusion of a microtubular cathode support and subsequent surface coatings with electrolyte and anode slurries. The GDC/ScSZ bilayer electrolyte was obtained on the LSM support using a cosintering technique, and the LSM-supported microtubular solid oxide fuel cells (SOFCs) were evaluated using field-emission scanning electron microscopy, X-ray diffraction, and electrochemical measurements in wet hydrogen (3% H 2 O) atmosphere. An LSM-GDC activation layer was also introduced between the cathode tube and the electrolyte layers for improvement of cell performance. The micro-SOFC exhibited a stable open-circuit voltage above 1.03 V in the temperature range from 450 to 750°C, and the cell generated a maximum power density of 15, 73, 230, and 378 mW/cm 2 at 500, 600, 700, and 750°C, respectively. This result indicates that our developed cosintering fabrication technology can realize a stable and high-performance, LSM-supported micro-SOFC.

Development and Evaluation of a Cathode-Supported SOFC Having a Honeycomb Structure

We report the designing and evaluation of a cathode-honeycomb-supported solid oxide fuel cell (SOFC), capable of generating high volumetric power density. The numerical analyses showed that the cathode-honeycomb-supported SOFC can be the most efficient form with the lowest current collection loss, as compared with the electrode- or anode-honeycomb-supported ones. The cathode-honeycomb-supported SOFC, which was fabricated via the extrusion of a LaSrMnO 3 honeycomb monolith and the channel surface coating by our developed wet process using electrolyte/anode bilayers, exhibited the high volumetric power density above 1 and 2 W/cm 3 at 600 and 650°C, respectively, under a wet H 2 fuel flow.

Demonstration of the Rapid Start-Up Operation of Cathode-Supported SOFCs Using a Microtubular LSM Support

The performance of a cathode-supported solid oxide fuel cell (SOFC) was improved by using a microtubular LaSrMnO 3 (LSM) support. The cell had a laminated structure, with a bilayer of dense gadolinium-doped ceria (GDC) layer and scandia-stabilized zirconia as the electrolyte and a NiO-GDC layer as the anode on the microtubular LSM support. It was fabricated by extrusion of the cathode support and subsequent surface coating by a wet process. Microstructural observations and electrochemical analyses showed that the cell has a stable and durable structure for rapid start-up operation at a heating rate of 60°C/min.

Effects of Anode Microstructure on the Performances of Cathode-Supported Micro-SOFCs

The effect of anode microstructure on the electrochemical performance of cathode-supported micro solid oxide fuel cells (SOFCs) was evaluated using current-voltage and ac impedance measurements. Small-scale cells were fabricated by the extrusion of a microtubular (La 0.8 Sr 0.2 ) 0.97 MnO 3 support and subsequent surface coating with a Ce 0.9 Gd 0.1 O 1.95 /Sc 2 O 3 -doped ZrO 2 bilayer electrolyte and NiO-Ce 0.9 Gd 0.1 O 1.95 anode layers. Impedance analysis and scanning electron microscopy observations indicate that an anode layer with coarse NiO particles has a higher porosity and electrode activity than that with fine NiO particles. The SOFC with coarse NiO particles generated more than twice the power density of that with fine NiO particles.

Novel Electrode-Supported Honeycomb Solid Oxide Fuel Cell: Design and Fabrication

We have developed a novel and highly effective electrode-supported solid oxide fuel cell (SOFC) with honeycomb structure for intermediate temperature operation. Honeycomb-supported SOFC is known as one of the most compact SOFCs due to the large electrode area per unit volume, which is attractive with regard to space saving and cost reduction. In this study, we summarized the design of the channel shape, size, and sequence using numerical simulation and techrcologies to realize the designed honeycomb SOFC fabrication. The calculation results showed that the wall thickness and the channel size of the honeycomb had to be less than 0.22 mm and more than 0.3 mm, respectively, for the sufficient net channel surface and the acceptable pressure drop. Also, a cathode-honeycomb-supported SOFC can be the more efficient form with lower current collection resistance, as compared with the anode-supported type. The actual fabricated honeycomb SOFC exhibited a high volumetric power density above 1 W/cm 3 at 650°C under wet H 2 fuel flow.

Development of Honeycomb-type SOFCs with Accumulated Multi Micro-cells

SOFC based on honeycomb support is known as one of the most compact SOFCs due to its large electrode area per a unit volume, which is attractive with regard to space saving, cost reduction and thermal control. In this study, the effects of material configuration and honeycomb channel number on the performance of SOFC were investigated using the simulation of equivalent electrical circuit. It was revealed that cathode- supported honeycomb type could be better for maximizing net electrode area per a unit volume and minimizing current collecting loss than any other types such as electrolyte- or anode-supported types due to its small current collecting loss.