Severine Ramousse

Performance and Durability of Solid Oxide Electrolysis Cells

Solid oxide fuel cells produced at Riso National Laboratory have been tested as electrolysis cells by applying an external voltage. Results on initial performance and durability of such reversible solid oxide cells at temperatures from 750 to 950°C and current densities from -0.25 A/cm 2 to - 0.50 A/cm 2 are reported. The full cells have an initial area specific resistance as low as 0.27 Ωcm 2 for electrolysis operation at 850°C. During galvanostatic long-term electrolysis tests, the cells were observed to passivate mainly during the first ∼ 100 h of electrolysis. Cells that have been passivated during electrolysis tests can be partly activated again by operation in fuel cell mode or even at constant electrolysis conditions after several hundred hours of testing.

Degradation of Anode Supported SOFCs as a Function of Temperature and Current Load

The degradation behavior of anode supported solid oxide fuel cells (SOFCs) was investigated as a function of operating temperature and current density. Degradation rates were defined and shown to be mainly dependent on the cell polarization. The combination of a detailed evaluation of electrochemical properties by impedance spectroscopy, in particular, and post-test microscopy revealed that cathode degradation was the dominant contribution to degradation at higher current densities and lower temperatures. The anode was found to contribute more to degradation at higher temperatures. Generally, the degradation rates obtained were lower at higher operating temperatures, even at higher current densities. A degradation rate as low as 2%/1000 h was observed at 1.7 A/cm 2 and 950°C over an operating period of 1500 h.

Nanostructured Lanthanum Manganate Composite Cathode

Anode-supported cells were fabricated with optimized cathodes showing high power density of 1.2 W/cm2 at 800°C under a cell voltage of 0.7 V and an active area of 4 4 cm. A microstructure study was performed on such cell using a field-emission gun scanning electron microscope, which revealed that the La1−xSrx yMnO3± LSM composite cathodes consist of a network of homogenously distributed LSM, yttria-stabilized zirconia YSZ , and pores. The individual grain size of LSM or YSZ is approximately 100 nm. The degree of contact between cathode and electrolyte is 39% on average.

Thermal Characterisation of Brake Pads

The chemical-physical decomposition processes that occur in a brake pad heated to 1000°C have been studied. This temperature can be reached when a brake pad is applied. Thermogravimetry and differential thermal analysis were used in combination with evolved gas analysis, and image analysis using a scanning electron microscope.A brake pad is essentially a mixture of iron, carbon and binder. Combined techniques have been used,because of chemical reaction overlap, to determine how and at what temperature the binder decomposes, the coal and graphite combust and the iron oxidises.This work enables the development of brake pads that are stable at high temperature.

Status of Development and Manufacture of Solid Oxide Fuel Cell at Topsoe Fuel Cell A/S and Riso̸/DTU

and Risø/DTU DTU Orbit (01/04/2019) Status of Development and Manufacture of Solid Oxide Fuel Cell at Topsoe Fuel Cell A/S and Risø/DTU Fuel Cell (TOFC) provides the SOFC technology platform: Cells, stacks, and integrated stack module for different applications and collaborates with integrator partners to develop, test and demonstrate SOFC applications. The technology development is based on a R&D consortium with Risø National Laboratory (Risø/DTU) which includes material synthesis and cost effective ceramic manufacturing methods for anode and metal supported flat planar cells in addition to multilayer assembling for compact stacks with metallic interconnects. The development is focussing on high electrochemical performance and durability as well as maximal robustness. In 2008 TOFC has constructed a 5 MW/year cell and stack production facility in Denmark featuring all the necessary unit operations from ceramic powder, continuous tape casting, screen printing, spray painting and sintering to complete stack modules. TOFCs engagement in SOFC technology includes system development in collaboration with system partners and development and manufacturing of integrated stack assemblies called PowerCore. ©2009 COPYRIGHT ECS The Electrochemical Society

Metal-Supported SOFC with Ceramic-Based Anode

Metal-supported solid oxide fuel cells have shown promise to offer several potential advantages over conventional anode (Ni-YSZ) supported cells, such as increased resistance against mechanical and thermal stresses and a reduction in materials cost. The purpose of this work is to illustrate how the metal-supported cell concept can be combined with ceramic-based anode materials, such as Nb-doped SrTiO3. The paper shows that a metal-supported cell can have excellent performance by only having electronically conducting phases in the anode backbone structure, into which electrocatalytically active materials are infiltrated after sintering. Initial area specific resistance as low as 0.3 Ωcm2 at 700 oC has been obtained with power densities > 1 Wcm-2. The initial results on the chemical compatibility, electrochemical performance, and galvanostatic durability of a ceramic based (Nb-doped SrTiO3), zirconia-free anode, in a planar metal-supported SOFC concept is discussed.