Sputtering of thin electrolyte layers has been demonstrated to increase solid oxide fuel cell (SOFC) performance in very small-scale, e.g., button cells. The few cases where thin film techniques were brought in to early stages of commercialization (e.g., Lilliputian and SiEnergy) showed remarkable low temperature SOFC performance, but required sophisticated cell designs processed with Si and MEMs type technologies. This work takes advantage of low cost, conventional ceramic processing to build large format (10 cm x 10 cm) half-cells upon which the sputtered layers above are added to dramatically increase SOFC performance. In this work, an electron-blocking layer which increases the open circuit cell voltage of the GDC electrolyte based cell and a Gd doped ceria (GDC) buffer layer which mitigates reactions between the cathode and electron blocking layer are deposited by sputtering. This presentation will present progress towards developing increased SOFC performance using this sputtering technology at the commercial-scale. Challenges encountered or expected with thin film development for SOFC commercialization will be discussed.

This study investigates the effect of thermal activation of all-vanadium redox flow battery (RFB) carbon-felt electrodes on their electrode kinetics. Using X-ray photoelectron spectroscopy, thermal activation is shown to increase the content of the C–OH group, decrease the content of the C═O group, and not affect the O–C═O group, with all these surface moieties already being present in the nonactivated carbon felt. Rotating disk electrode studies were performed using custom electrodes fabricated using the carbon felt to investigate the kinetics of the V2+/V3+ and VO2+/VO2+ redox couples in H2SO4 and to deconvolute the impact of thermal activation on electrode kinetics. We demonstrate that V2+/V3+ kinetics is sluggish compared to VO2+/VO2+ kinetics (equilibrium rate constant (k0) = 4.98 × 10–8 m·s–1 vs 8.81 × 10–8 m·s–1) and that thermal activation enhanced V2+/V3+ kinetics while inhibiting VO2+/VO2+ kinetics. The enhancement in V2+/V3+ kinetics was attributed to the oxygen-containing groups −C–OH added du...

As part of an effort to build a prototype flow battery system using a nano-suspension containing β-Ni(OH)2 nanoparticles as the cathode material, nano-sized β-Ni(OH)2 particles with well-controlled particle size and morphology were synthesized via the one-step precipitation of a NiCl2 precursor. The composition and morphology of the nanoparticles were characterized by scanning electronic microscopy (SEM) and X-ray diffraction (XRD). The XRD patterns confirmed that β-Ni(OH)2 was successfully synthesized, while SEM results showed that the particle sizes range from 70 to 150 nm. To ensure that Ni(OH)2 could be employed in the nano-suspension flow battery, the electrochemical performance of the synthesized β-Ni(OH)2 was initially tested in pouch cells through charge/discharge cycling. The phase transformations occurring during charge/discharge were investigated usingin-situ X-ray absorption spectroscopy to obtain the shift in the oxidation state of Ni (X-ray adsorption near edge structure, XANES) and the distances between Ni and surrounding atoms in charged and discharged states (extended X-ray absorption fine structure, EXAFS). XANES results indicated that the electrode in the discharged state was a mixture of phases because the edge position did not shift back completely. XAFS results further proved that the discharge capacity was provided by β-NiOOH and the ratio between β-Ni(OH)2 and g-NiOOH in the electrode in the discharged state was 71:29. Preliminary nano-suspension tests in a lab-scale cell were conducted to understand the behavior of the nano-suspension during charge/discharge cycling and to optimize the operating conditions.

The Direct Carbon Fuel Cell (DCFC), which uses solid carbon as fuel and molten carbonate as electrolyte, has had resurgence of interest due to very high electrochemical conversion efficiency, nearly 100%, no requirement of fuel reforming, and potential for CO 2 capture and sequestration. At the cathode, carbon dioxide is converted into carbonate ions. The main reaction at the anode is generation of carbon dioxide from carbon and carbonate, the net cell reaction being oxidation of carbon to carbon dioxide. Additional reactions that may be occur at the anode are a two-electron reaction resulting in co-generation of carbon dioxide and carbon monoxide and the Boudouard reaction leading to conversion of carbon and carbon dioxide to carbon monoxide, the so-called “carbon corrosion”. The performance of DCFC can be appreciably limited by this reaction. The reverse Boudouard reaction has not been studied in solid-melt-gas systems. It is important to study this reaction in conjunction with wetting behavior of carbon in molten carbonate. With this in mind, the wetting behavior of carbon electrode in molten carbonate, comprised of a Li-K eutectic mixture, was studied in this study at different temperatures. The wetting behavior is complicated due to reactions occurring at the carbon surface before or after the start of wetting. Before wetting, carbon rods were exposed to a gas atmosphere with varying partial pressures of carbon dioxide to examine the extent of Boudouard reaction and the resulting structural changes in carbon rods. This reaction modifies the lateral surface of carbon electrode due to carbon corrosion, which leads to reduction in interfacial tension between solid carbon and molten carbonate after dipping carbon rods in molten carbonate. Wetting behavior of carbon rods was studied for a period of 24 hours. The effects of temperature and pre-exposure to varying levels of carbon dioxide on speed of formation of liquid (molten carbonate) meniscus, propagation of liquid film thereafter, and the ultimate length of liquid film were studied. During the wetting process, bubble evolution occurred at the surface of carbon electrode not only below the meniscus, but also above the meniscus. This indicates that wetting of carbon electrode in molten carbonate is influenced not only by capillary forces but also by the reverse Boudouard reaction. The reverse Boudouard reaction is promoted at higher temperature, leading to changes to greater extent in the surface structure and therefore solid-liquid and solid-vapor interfacial tensions. The lateral surfaces of graphite rods before wetting and after wetting, liquid films formed on the graphite rods, and cross-sections of cylindrical carbon rods above and below the meniscus were analyzed using SEM. The liquid films and circular cross-sections of carbon rods were also analyzed using energy-dispersive X-ray spectroscopy (EDX) and distributions and variations in oxygen and potassium were examined. Oxide ions are generated prior to and during wetting of carbon rods and play an important role in surface modification of these prior to and during wetting. A reaction mechanism based on the experimental observations is proposed. The roles of Boudouard reaction, including equilibrium characteristics, and oxide ions on surface modification of carbon rods before and after wetting and the implications thereof on wetting behavior of carbon rods are explained satisfactorily by the reaction mechanism.