Anthony Wood

Recent progress in the performance of intermediate temperature (500–600°C) protonic ceramic fuel cells (PCFCs) has demonstrated both fuel flexibility and increasing power density that approach commercial application requirements. Under the U.S. DOE ARPA-E REBELS program, the Colorado School of Mines (Mines), in collaboration with Fuel Cell Energy (FCE), is developing durable, kW-scale PCFC stacks and system concepts. Results from cell scale-up efforts are reviewed. Several cells have been tested for over 6,000 hours, and we demonstrate excellent performance and exceptional durability (<1.5%/1,000 hours in most cases) across all fuels without any modifications in the cell composition or architecture. The success of scale-up efforts towards commercially viable, kW-scale cell platforms is given, inclusive of short stack test results. System-level work shows that trade-offs between lower cell power densities (due to lower operating temperature), lower-cost materials, manufacturing processes, and balance-of-stack components exist which can offer competitive advantage for PCFCs in various stationary power applications.

Planar-type solid oxide fuel cells (SOFCs) developed at Versa Power Systems (VPS) demonstrate high performance, low degradation rates and are well-positioned to meet commercial targets. These cells also perform well when operating reversibly in electrolysis mode for hydrogen production, and remarkable current densities in excess of 6 A/cm² have been achieved at 800°C with a cell voltage of < 1.67 V. In the present study the effect of operating conditions on degradation rate were investigated, including temperature, current density and steam utilization. The evolution of V - J performance and electrochemical impedance spectroscopy after long-term testing at constant current density is presented and degradation effects analyzed.

Solid Oxide Electrolysis (SOE) can be used to produce hydrogen with very high efficiencies at remarkable hydrogen production rates. Through microstructural and compositional modification, conventional low cost Solid Oxide Fuel Cell (SOFC) materials have been used to create a Solid Oxide Electrolysis Cell (SOEC) that can achieve remarkable current density at cell voltages allowing higher conversion efficiency than current commercial electrolysers. Current densities in excess of 6 A/cm² have been achieved at 800°C with a cell voltage of < 1.67 V. This cell shows a more than 3-fold increase in hydrogen production rate at higher efficiency than established commercial electrolysers.

Versa Power Systems (VPS) is a developer of Solid Oxide Fuel Cell (SOFC) technology focused on SOFC stack development for commercial applications. In recent years VPS has been developing reversible SOFC (RSOFC) materials systems with a view to future commercial development of RSOFC stacks. VPS has demonstrated significant technical improvements in RSOFC materials technology in a relatively short timeframe, and has begun to test these at the stack level. This paper will provide an update of RSOFC activities including cell and stack testing in both steady-state electrolysis operation and operating with RSOFC cycles (fuel cell and electrolysis cycling).

The most commonly used solid oxide fuel cell (SOFC) anode material is a two-phase, nickel- and yttria-stabilized zirconia (Ni∕YSZ)(Ni∕YSZ) cermet. During fuel cell operation, this material is exposed to a reducing environment and thus remains a cermet; however, the metallic component of the anode may reoxidize in a commercial SOFC system. Following an initial study of the redox kinetics and dimensional changes after reduction and oxidation, as well as a baseline characterization of the electrochemical performance degradation and microstructural changes after redox cycling, two modifications to the anode microstructure were made in order to enhance cell redox tolerance: the anode functional layer was functionally graded and an oxidation barrier layer was added to the bottom of the cell in order to restrict the ability of oxygen to flow into the anode. Both types of microstructural modification significantly improved the cell redox tolerance compared with standard baseline redox tests.