Development of Metal-Supported SOFC toward Durable, Highly Efficient and Cost-effective Electrochemical Energy Conversion Systems

Kurzfassung

Solid Oxide Fuel Cell (SOFC) is widely acknowledged for a highly efficient energy conversion and fuel flexibility. The variety of potential applications of SOFC should also be remarked, e.g. reversible operation for steam electrolysis producing hydrogen from steam and electricity. Cost effectiveness and high energy conversion efficiency of SOFCs are attractive in renewable energy technologies. Research activities in the SOFC group at DLR are dedicated to the development of cost-effective SOFC stacks of high performance and high durability based on metal supported (MS) SOFCs. The MS-SOFC architecture offers intrinsically superior mechanical strength to anode supported SOFCs. Inexpensive porous metal will increase the robustness of the cell, which improves durability, tolerance to redox cycling and fast start-up capability, while the cell architecture can reduce the needs for critical raw materials. For MS cell fabrication, various coating technologies have been demonstrated, including thermal spraying, wet chemical processes, and physical vapour deposition. In the European project EVOLVE (FCH JU Grant 303429-2012/2017) MS-SOFCs have been successfully demonstrated, implementing a few micro meter thick gas-tight electrolyte coating by physical vapour deposition (PVD) and being manufactured at temperatures below 1000C in order to prevent metal support degradation. Another challenge is to apply our MS-SOFC technologies to develop proton conducting ceramic cells (PCC). While steam is supplied and wet hydrogen is extracted simultaneously at the hydrogen electrode in SOFC-based steam electrolysis cells, steam supply and pure hydrogen production occur exclusively at the oxygen electrode and the fuel electrode, respectively, in PCC-based electrolysis cells. This geometry of PCC may reduce oxidation and other corrosion phenomena at the fuel electrode and maximizes the fuel utilization by avoiding dilution of the fuel with the product of reaction. One of the key challenges for MS-PCCs is the coating process of gas-tight electrolyte layer without any high temperature thermal treatment, which is usually much higher than 1000C in the case of ceramic supported PCCs. The manufacturing strategy specifically designed for MS-SOFCs as well as MS-PCCs will be discussed.