Development of Metal-Supported Proton-Conducting Solid Oxide Cells Via Co-Sintering

Abstract

Use of proton conducting electrolytes in solid oxide fuel cells (SOFCs) and electrolysis cells (SOECs) enables efficient operation at lower temperatures, reducing thermal stress and allowing the use of less expensive stack materials and balance-of-plant components. Transport of protons across the electrolyte offers other advantages: for electrolysis, pure hydrogen is produced so steam does not need to be removed; for fuel cell operation, extraction of hydrogen from the anode through the electrolyte drives fuel decomposition or reforming reactions. Proton conducting oxide electrolyte materials could potentially lower the operating temperature of metal-supported solid oxide cells (MS-SOCs) to the intermediate range 400 to 600 °C. The metal substrate provides the advantages such as high thermal and redox cycling tolerance, low-cost of structural materials, and mechanical ruggedness.In this work, co-sintering fabrication of metal-supported proton conducting solid oxide cells using BaZr1-x-yCexYyO3-δ (BZCY) is developed. BZCY ceramics are sintered in reducing environment supported on stainless steel metal support. Critical challenges for this fabrication approach include: contamination of the electrolyte with Si and Cr from the metal support, incomplete electrolyte sintering, and evaporation of Ba from the electrolyte. Lowering the sintering temperature to 1350°C alleviates these challenges. The use of LiF and Mn-oxide as sintering aids achieve electrolyte densification at this low temperature. Nevertheless, shrinkage matching of the stainless steel and ceramic layers during sintering is very challenging. Various efforts will be discussed, including optimization of the ceramic sintering aid loading, impact of metal particle size, and thermal manipulation of the ceramic powder surface. Successful co-sintering of a symmetric cell is achieved.