Carbon-Free Hydrogen Production in a Steam-Carbon Electrochemical Cell

Alexander, Brentan R.; Lee, Andrew; Mitchell, Reginald E.; Gür, Turgut M.

doi:10.1149/1.3501096

Cited by 8 publications

(11 citation statements)

References 22 publications

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“…Instead, the steam-carbon fuel cell concept provides a thermodynamically downhill process for spontaneous generation of hydrogen (and cogeneration of electrical power). More recently, the steam-carbon fuel cell concept was demonstrated experimentally, − where the carbon compartment is physically separated from the H 2 /steam stream by the impervious YSZ solid electrolyte, thus requiring no further need for expensive separation processes otherwise required to remove CO and CO 2 from the H 2 stream as is the case for reformation processes. The steam-carbon fuel cell concept is schematically illustrated in Figure .…”

Section: Carbon Utilization and Conversion In Cfcsmentioning

confidence: 99%

Critical Review of Carbon Conversion in “Carbon Fuel Cells”

2013

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Section: Carbon Utilization and Conversion In Cfcsmentioning

confidence: 99%

Critical Review of Carbon Conversion in “Carbon Fuel Cells”

2013

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“…Previous work on the SCFC concept operating on activated carbon in our lab has shown peak power densities in excess of 220 mW/cm 2 , obtained with a commercial anode-supported tubular cell (Materials and Systems Research, Inc. of Salt Lake City, UT) with optimized cell components, including a 10μm thin YSZ electrolyte membrane and electrodes of better morphology. [30][31][32] This comparison clearly suggests that the SCFC device used in this study is limited by sub-optimal electrode morphology and a thick electrolyte.…”

Section: Anode Gas Flow Inletmentioning

confidence: 80%

Experimental and Modeling Study of Biomass Conversion in a Solid Carbon Fuel Cell

Alexander¹,

Mitchell²,

Gür³

2012

J. Electrochem. Soc.

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Pulverized samples of charred biomass from rice straw, wood, almond shell, and corn stover were converted within a solid carbon fuel cell (SCFC) using a yttria stabilized zirconia oxide ion conducting electrolyte. Open circuit cell potentials against air for all solid fuels tested at 900 • C were in the range 1.00 to 1.07 V, in good agreement with expected values. Measurements of cell performance indicated peak power densities of 34 to 39 mW/cm 2 for the biomass fuels, which compared favorably with a peak power density of 38 mW/cm 2 for an activated carbon fuel used for benchmarking purposes. Comparison with previous measurements for activated carbon in our laboratory, where peak power densities in excess of 220 mW/cm 2 were demonstrated in optimized cells, suggests great promise for biomass utilization in a SCFC. Further modeling of corn stover and activated carbon revealed that the lower specific surface area and bulk density of the biomass chars is offset by a higher fuel reactivity in the dry gasification environment inside the SCFC anode compartment. The modeling also defined the limits of the SCFC operating window for high effective char utilization and demonstrated that high current densities can be supported when biomass chars are employed.

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“…The steam-carbon fuel cell concept proposed earlier by the authors [30][31][32] was investigated further in this paper. It is a modification of the fluidized bed direct carbon fuel cell (FB-DCFC) concept [25][26][27][28][29] and employs a solid oxide fuel cell configuration.…”

Section: Description Of the Steam-carbon Fuel Cell Conceptmentioning

confidence: 99%

“…23,24 Ongoing work in our laboratory, built on previous studies focusing on an air-carbon fuel cell arrangement, [25][26][27][28][29] has recently demonstrated the feasibility of using a steam-carbon electrochemical cell for carbon-free hydrogen production. 30,31 The steam-carbon cell employs a YSZ electrolyte, steam at the cathode compartment, and a bed of solid carbonaceous fuel at the anode compartment. This arrangement not only eliminates the OCV completely, but also reverses the sign of the cell potential such that the cell operates as a fuel cell.…”

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confidence: 99%

“…Motivated by the earlier work, [30][31][32] this paper reports the results of an experimental study of a steam-carbon electrochemical cell, which imitates the steam reforming reaction of carbon, with the exception that the reactant and product streams in this configuration are physically separated by the solid electrolyte membrane, and do not mix with each other.…”

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Steam-Carbon Fuel Cell Concept for Cogeneration of Hydrogen and Electrical Power

Alexander¹,

Mitchell²,

Gür

2011

J. Electrochem. Soc.

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This study describes and presents the results of a new electrochemical approach to co-production of hydrogen and electric power using a steam-carbon fuel cell, within which carbon-containing species are kept physically separate from the hydrogen stream by a solid oxide electrolyte membrane. The fuel cell used for this purpose consists of H 2 , H 2 O (g) /Pt/YSZ/Pt/C (s) ,CO,CO 2 and measurements are taken between 600 and 900 C. Peak electrical power generated at 900 C is 8 mW/cm 2 at a current density of 40.5 mA/ cm 2 corresponding to simultaneous production of carbon-free hydrogen at a rate of 354 g H 2 /m 2 day. Electrochemical behavior and cell loss mechanisms are studied using impedance spectroscopy in different cell arrangements operating in steam-carbon and air-carbon modes. Exchange current densities extracted from these measurements indicated activation energies of 80.3 6 7.9 kJ/ mol for oxygen reduction, 132 6 12 kJ/mol for CO oxidation, and 189 6 35 kJ/mol for steam reduction. These results indicate that steam reduction is the dominant loss mechanism with significant contribution from CO oxidation kinetics. Modeling results for the carbon bed indicate that a bed height of 7 mm is capable of supporting cell current densities of 700 mA/cm 2 at 85% effective char utilization, allowing for high performing steam-carbon fuel cells for the simultaneous production of hydrogen and electrical work. Hydrogen is a desirable fuel because it is both an effective energy carrier as well as a clean burning fuel with minimal impact on the environment. Unfortunately, hydrogen does not occur naturally, and must be generated from other sources. If widespread use of hydrogen is to be achieved, an efficient method for distributed hydrogen production is desired due to the cost and technical challenges posed by hydrogen transportation and storage.Currently, the majority of hydrogen production is performed centrally using steam reforming of methane, and to a lesser extent, coal. The fuel is reformed with steam and then undergoes the water-gas shift reaction to produce hydrogen. Unfortunately, this process produces a hydrogen stream that is contaminated by various carbonaceous species, and therefore requires expensive separation techniques to clean the gas. Carbon monoxide remnants in the hydrogen gas are of particular concern, as even trace amounts of CO in the hydrogen stream render the hydrogen product undesirable for catalytic processes due to CO poisoning. This is a critical problem especially for low temperature fuel cells. In addition, the reforming process is only economically feasible at large scales, requiring expensive storage and distribution of the hydrogen product to its point of use.A variety of alternative hydrogen production schemes that attempt to solve or avoid the limitations of reforming have been proposed. Thermal decomposition of steam into hydrogen and oxygen is one such option, but this reaction is thermodynamically uphill and energetically expensive. Another approach is the electrolysis of water in an e...

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Carbon-Free Hydrogen Production in a Steam-Carbon Electrochemical Cell

Cited by 8 publications

References 22 publications

Critical Review of Carbon Conversion in “Carbon Fuel Cells”

Critical Review of Carbon Conversion in “Carbon Fuel Cells”

Experimental and Modeling Study of Biomass Conversion in a Solid Carbon Fuel Cell

Steam-Carbon Fuel Cell Concept for Cogeneration of Hydrogen and Electrical Power

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