Pacific Northwest National Laboratory
Energy Science and Technology Directorate

SOFC Research and Development at PNNL

PNNL has been working with government agencies, industries, and academic institutions since 1987 to assist in the development of solid oxide fuel cell (SOFC) technology. SOFC R&D development activities at PNNL cover a wide range of technology development, testing, and optimization activities, including development of cell and stack materials, cell/stack/system modeling and design, fuel processing, and balance-of-plant component design. In addition to these activities, PNNL is a co-leader (with the National Energy Technology Laboratory (NETL)) of the Department of Energy's Solid-State Energy Conversion Alliance (SECA) initiative. The goal of SECA is to accelerate the development of commercial, low-cost 3 to 10-kW SOFC power systems. PNNL and NETL manage the SECA Core Technology Development Program (CTP), which coordinates SOFC development activities at numerous universities, national laboratories and other research institutions. Through technical meetings and workshops, the SECA CTP works with SECA industry teams to identify, prioritize, and solve technical barriers to SOFC commercialization.

SOFC Materials Development at PNNL

SECA Core Technology Program (SECA-CTP): Through its participation in the SECA Core Technology Program, PNNL is investigating materials degradation processes and developing materials for solid oxide fuel cells and stacks. The primary goal of these activities is to meet the cost, performance, and life-time targets of SECA-derived SOFC power generation systems.

Summary of recent CTP component materials development activities:

  • Evaluation of corrosion processes in alloy interconnects - PNNL is engaged in an in-depth study of oxidation and corrosion processes occurring in alloy interconnects under SOFC operating conditions. Ferritic stainless alloys, Ni-base alloys and other alloys are being studied under "dual atmosphere" exposure conditions representative of the SOFC interconnect environment. Simultaneous exposure of the alloys to oxidizing and reducing atmospheres resulted in accelerated corrosion and metal loss when compared to exposure to either oxidant or reductant environments.

  • Seal development - PNNL is developing several sealing technologies for SOFC stacks. Promising seal approaches include glass-ceramic seals, compressive mica-based seals, reactive air brazes, and engineered compliant seals. Glass-ceramic seal development efforts are focusing on evaluation of the effects of glass composition and sealing temperature on the thermal expansion, long-term stability and thermal cycle stability of seals and seal/component interfaces. Compressive seals allow for effective sealing of stack components having significant thermal expansion mismatch. Reactive air brazing (RAB) compositions, which allow for sealing under ambient conditions, are being evaluated for long-term stability in dual atmosphere (air/fuel) environments.

  • Anode materials - Ceramic anode materials in the Sr-La-Ti-Ce-O system developed at PNNL have demonstrated low anodic polarization and excellent resistance to sulfur, carbon formation, and thermal / red-ox cycling.

  • Cathode materials - Mixed conducting cathodes, such as LSCF, are being investigated in an effort to increase cell power density and stability at intermediate operating temperatures (650-800°C). State-of-the-art LSM cathodes are also being optimized for improved performance.

  • Interconnect/cathode interactions - Tests at PNNL have demonstrated that under some circumstances, Cr vapor species such as CrO3 and CrO2(OH)2 volatilized from chromia-forming alloy interconnects can lead to severe degradation of cathode performance. In addition to performing studies intended to quantify and understand the poisoning phenomenon, PNNL is developing optimized cathode/interconnect interfacial materials. Development efforts are focused on modifications to alloy interconnect surfaces, such as spinel coatings, to mitigate Cr volatilization, improve scale conductivity, and reduce oxidation kinetics.

    • High Temperature Electrochemistry Center: Montana State University, the University of Florida, the University of Utah, the National Energy Technology Laboratory, and PNNL are participants in the High Temperature Electrochemistry Center, supported by the US DOE's Office of Fossil Energy. Objectives of the Center are to advance solid oxide technology relevant to needs in Distributed Generation (DG) and FutureGen applications, through the development of solid oxide fuel cells, high temperature electrolyzers, reversible fuel cells, energy storage devices, gas separation membranes, thermoelectric materials, and electrochemical sensors. The Center also conducts fundamental research that aids the general development of all solid oxide technologies.

    Collaborations with Industry: PNNL is currently engaged in several collaborative technology development efforts with SOFC manufacturers. PNNL's extensive knowledge base in the areas of materials synthesis and characterization, cell and stack testing, design optimization, fuel processing and catalysis provides a strong basis for solving specific challenges faced by SOFC system developers. As an example of industrial collaboration, scientists and engineers in PNNL's materials division are working closely with the Delphi Corporation/BMI SECA team to develop an SOFC-based auxiliary power unit for military and transportation applications. The Delphi-Battelle team just recently passed the SECA Phase 1 demonstration trial, in which an APU system was run for 1500 hours with less than 7% power degradation.