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First-principles-based reaction kinetics from reactive molecular dynamics simulations: Application to hydrogen peroxide decomposition. Proc Natl Acad Sci U S A 2018; 116:18202-18208. [PMID: 30242137 DOI: 10.1073/pnas.1701383115] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
This paper presents our vision of how to use in silico approaches to extract the reaction mechanisms and kinetic parameters for complex condensed-phase chemical processes that underlie important technologies ranging from combustion to chemical vapor deposition. The goal is to provide an analytic description of the detailed evolution of a complex chemical system from reactants through various intermediates to products, so that one could optimize the efficiency of the reactive processes to produce the desired products and avoid unwanted side products. We could start with quantum mechanics (QM) to ensure an accurate description; however, to obtain useful kinetics we need to average over ∼10-nm spatial scales for ∼1 ns, which is prohibitively impractical with QM. Instead, we use the reactive force field (ReaxFF) trained to fit QM to carry out the reactive molecular dynamics (RMD). We focus here on showing that it is practical to extract from such RMD the reaction mechanisms and kinetics information needed to describe the reactions analytically. This analytic description can then be used to incorporate the correct reaction chemistry from the QM/ReaxFF atomistic description into larger-scale simulations of ∼10 nm to micrometers to millimeters to meters using analytic approaches of computational fluid dynamics and/or continuum chemical dynamics. In the paper we lay out the strategy to extract the mechanisms and rate parameters automatically without the necessity of knowing any details of the chemistry. We consider this to be a proof of concept. We refer to the process as RMD2Kin (reactive molecular dynamics to kinetics) for the general approach and as ReaxMD2Kin (ReaxFF molecular dynamics to kinetics) for QM-ReaxFF-based reaction kinetics.
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Sasaki K, Takahashi I, Kuramoto K, Tomomichi K, Terai T. Reactions on Ni-YSZ cermet anode of solid oxide fuel cells during internal steam reforming of n-octane. Electrochim Acta 2018. [DOI: 10.1016/j.electacta.2017.10.135] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Jaworski Z, Zakrzewska B, Pianko-Oprych P. On thermodynamic equilibrium of carbon deposition from gaseous C-H-O mixtures: updating for nanotubes. REV CHEM ENG 2017. [DOI: 10.1515/revce-2016-0022] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
AbstractExtensive literature information on experimental thermodynamic data and theoretical analysis for depositing carbon in various crystallographic forms is examined, and a new three-phase diagram for carbon is proposed. The published methods of quantitative description of gas-solid carbon equilibrium conditions are critically evaluated for filamentous carbon. The standard chemical potential values are accepted only for purified single-walled and multi-walled carbon nanotubes (CNT). Series of C-H-O ternary diagrams are constructed with plots of boundary lines for carbon deposition either as graphite or nanotubes. The lines are computed for nine temperature levels from 200°C to 1000°C and for the total pressure of 1 bar and 10 bar. The diagram for graphite and 1 bar fully conforms to that in (Sasaki K, Teraoka Y. Equilibria in fuel cell gases II. The C-H-O ternary diagrams. J Electrochem Soc 2003b, 150: A885–A888). Allowing for CNTs in carbon deposition leads to significant lowering of the critical carbon content in the reformates in temperatures from 500°C upward with maximum shifting up the deposition boundary O/C values by about 17% and 28%, respectively, at 1 and 10 bar.
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Hansen JB. Fuel processing for fuel cells and power to fuels as seen from an industrial perspective. J Catal 2015. [DOI: 10.1016/j.jcat.2015.04.014] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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Merinov BV, Mueller JE, van Duin ACT, An Q, Goddard WA. ReaxFF Reactive Force-Field Modeling of the Triple-Phase Boundary in a Solid Oxide Fuel Cell. J Phys Chem Lett 2014; 5:4039-4043. [PMID: 26276491 DOI: 10.1021/jz501891y] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
In our study, the Ni/YSZ ReaxFF reactive force field was developed by combining the YSZ and Ni/C/H descriptions. ReaxFF reactive molecular dynamics (RMD) were applied to model chemical reactions, diffusion, and other physicochemical processes at the fuel/Ni/YSZ interface. The ReaxFF RMD simulations were performed on the H2/Ni/YSZ and C4H10/Ni/YSZ triple-phase boundary (TPB) systems at 1250 and 2000 K, respectively. The simulations indicate amorphization of the Ni surface, partial decohesion (delamination) at the interface, and coking, which have indeed all been observed experimentally. They also allowed us to derive the mechanism of the butane conversion at the Ni/YSZ interface. Many steps of this mechanism are similar to the pyrolysis of butane. The products obtained in our simulations are the same as those in experiment, which indicates that the developed ReaxFF potential properly describes complex physicochemical processes, such as the oxide-ion diffusion, fuel conversion, water formation reaction, coking, and delamination, occurring at the TPB and can be recommended for further computational studies of the fuel/electrode/electrolyte interfaces in a SOFC.
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Affiliation(s)
- Boris V Merinov
- †Materials and Process Simulation Center, California Institute of Technology, 1200 East California Boulevard, m/c 139-74, Pasadena, California 91125, United States
| | - Jonathan E Mueller
- †Materials and Process Simulation Center, California Institute of Technology, 1200 East California Boulevard, m/c 139-74, Pasadena, California 91125, United States
| | - Adri C T van Duin
- ‡Department of Mechanical and Nuclear Engineering, Pennsylvania State University, 136 Research Building East, University Park, Pennsylvania 16802, United States
| | - Qi An
- †Materials and Process Simulation Center, California Institute of Technology, 1200 East California Boulevard, m/c 139-74, Pasadena, California 91125, United States
| | - William A Goddard
- †Materials and Process Simulation Center, California Institute of Technology, 1200 East California Boulevard, m/c 139-74, Pasadena, California 91125, United States
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Pomfret MB, Walker RA, Owrutsky JC. High-Temperature Chemistry in Solid Oxide Fuel Cells: In Situ Optical Studies. J Phys Chem Lett 2012; 3:3053-3064. [PMID: 26292249 DOI: 10.1021/jz3012047] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Solid oxide fuels cells (SOFCs) are promising devices for versatile and efficient power generation with fuel flexibility, but their viability is contingent upon understanding chemical and material processes to improve their performance and durability. Newly developed in situ optical methods provide new insight into how carbon deposition varies with different hydrocarbon and alcohol fuels and depends on operating conditions. Some findings, such as heavier hydrocarbon fuels forming more carbon than lighter fuels, are expected, but other discoveries are surprising. For example, methanol shows a greater tendency to form carbon deposits than methane at temperatures below 800 °C, and kinetically controlled steam reforming with ethanol at high temperatures (∼800 °C) is less detrimental to SOFC performance than operating the device with dry methanol as the fuel. In situ optical techniques will continue to provide the chemical information and mechanistic insight that is critical for SOFCs to become a viable energy conversion technology.
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Affiliation(s)
- Michael B Pomfret
- †Chemistry Division, Naval Research Laboratory, Washington, DC 20375, United States
| | - Robert A Walker
- ‡Department of Chemistry and Biochemistry, Montana State University, Bozeman, Montana 59717, United States
| | - Jeffrey C Owrutsky
- †Chemistry Division, Naval Research Laboratory, Washington, DC 20375, United States
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Norinaga K, Yatabe H, Matsuoka M, Hayashi JI. Application of an Existing Detailed Chemical Kinetic Model to a Practical System of Hot Coke Oven Gas Reforming by Noncatalytic Partial Oxidation. Ind Eng Chem Res 2010. [DOI: 10.1021/ie100506v] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Koyo Norinaga
- Institute for Materials Chemistry and Engineering, Kyushu University, Fukuoka 816-8580, Japan, Coal Gasification System Center, Kure Division, Babcock-Hitachi K.K., Kure 737-8508, Japan, and R&D Center, Nippon Coke & Engineering Co., Ltd., Kitakyushu 808-0021, Japan
| | - Hiroshi Yatabe
- Institute for Materials Chemistry and Engineering, Kyushu University, Fukuoka 816-8580, Japan, Coal Gasification System Center, Kure Division, Babcock-Hitachi K.K., Kure 737-8508, Japan, and R&D Center, Nippon Coke & Engineering Co., Ltd., Kitakyushu 808-0021, Japan
| | - Masahiro Matsuoka
- Institute for Materials Chemistry and Engineering, Kyushu University, Fukuoka 816-8580, Japan, Coal Gasification System Center, Kure Division, Babcock-Hitachi K.K., Kure 737-8508, Japan, and R&D Center, Nippon Coke & Engineering Co., Ltd., Kitakyushu 808-0021, Japan
| | - Jun-ichiro Hayashi
- Institute for Materials Chemistry and Engineering, Kyushu University, Fukuoka 816-8580, Japan, Coal Gasification System Center, Kure Division, Babcock-Hitachi K.K., Kure 737-8508, Japan, and R&D Center, Nippon Coke & Engineering Co., Ltd., Kitakyushu 808-0021, Japan
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Pomfret MB, Owrutsky JC, Walker RA. In situ optical studies of solid-oxide fuel cells. ANNUAL REVIEW OF ANALYTICAL CHEMISTRY (PALO ALTO, CALIF.) 2010; 3:151-174. [PMID: 20636038 DOI: 10.1146/annurev.anchem.111808.073641] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Thermal imaging and vibrational spectroscopy have become important tools for examining the physical and chemical changes that occur in real time in solid-oxide fuel cells (SOFCs). Imaging techniques can resolve temperature differences as fine as 0.1 degrees C across a SOFC electrode at temperatures higher than 600 degrees C. Vibrational spectroscopy can identify molecular species and changes in material phases in operating SOFCs. This review discusses the benefits and challenges associated with directly observing processes that are important to SOFC performance and durability. In situ optical methods can provide direct insight into reaction mechanisms that can be inferred only indirectly from electrochemical measurements such as voltammetry and electrochemical impedance spectroscopy and from kinetic models and postmortem, ex situ examinations of SOFC components. Particular attention is devoted to recent advances that, hopefully, will spur the development of new generations of efficient, versatile energy-producing devices.
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Affiliation(s)
- Michael B Pomfret
- Chemistry Division, Naval Research Laboratory, Washington, District of Columbia 20375, USA
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Lo Faro M, La Rosa D, Nicotera I, Antonucci V, Aricò A. Electrochemical behaviour of propane-fed solid oxide fuel cells based on low Ni content anode catalysts. Electrochim Acta 2009. [DOI: 10.1016/j.electacta.2009.03.077] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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Direct Utilization of Liquid Fuels in SOFC for Portable Applications: Challenges for the Selection of Alternative Anodes. ENERGIES 2009. [DOI: 10.3390/en20200377] [Citation(s) in RCA: 100] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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Bessler WG, Gewies S, Vogler M. A new framework for physically based modeling of solid oxide fuel cells. Electrochim Acta 2007. [DOI: 10.1016/j.electacta.2007.08.030] [Citation(s) in RCA: 192] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Janardhanan VM, Deutschmann O. Numerical study of mass and heat transport in solid-oxide fuel cells running on humidified methane. Chem Eng Sci 2007. [DOI: 10.1016/j.ces.2007.01.043] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Wang S, Sheng Y, Feng M, Leszczynski J, Wang L, Tachikawa H, Yu H. Light-induced cytotoxicity of 16 polycyclic aromatic hydrocarbons on the US EPA priority pollutant list in human skin HaCaT keratinocytes: relationship between phototoxicity and excited state properties. ENVIRONMENTAL TOXICOLOGY 2007; 22:318-27. [PMID: 17497637 PMCID: PMC3764498 DOI: 10.1002/tox.20241] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/07/2023]
Abstract
The photocytotoxicity of 16 polycyclic aromatic hydrocarbons (PAHs) on the priority pollutant list of the United States Environmental Protection Agency (US EPA) were tested in human skin HaCaT keratinocytes. A selected PAH was mixed with HaCaT cells and irradiated with a solar simulator lamp for a dose equivalent to 5 min of outdoor sunlight and the cell viability was determined immediately and also after 24 h of incubation. For the cells without incubation after the treatments, it is found that all PAHs with three rings or less, except anthracene, are not photocytotoxic, while the four or five-ring PAHs (except chrysene), benz[a]anthracene, dibenzo[a,h]anthracene, benzo[ghi]perylene, benzo[a]pyrene, indeno[1,2,3-cd]pyrene, benzo[b]fluorenthene, fluorenthene, and pyrene, are photocytotoxic to the human skin HaCaT keratinocytes. If the cells were incubated for 24 h after the treatments, the photocytotoxic effect of the PAHs was greatly amplified in comparison to the nonincubated cells. For the 24 h incubated cells, all PAHs except naphthalene exhibit photocytotoxicity to some extent. Exposure to 5 microM of the 4- and 5-ring PAHs (except chrysene) and 3-ring anthracene more than 80% of the cells lose viability. The photocytotoxicity of the PAHs correlates well with several of their excited state properties: light absorption, excited singlet-state energy, excited triplet-state energy, and HOMO-LUMO energy gap. All the photocytotoxic PAHs absorb light at >300 nm, in the solar UVB and UVA region. There is a threshold for each of the three excited state descriptors of a photocytotoxic PAH: singlet energy <355 kJ/mol (corresponding to 337 nm light), triplet energy <230 kJ/mol (corresponding to 520 nm light), HOMO-LUMO gap <3.6 eV (corresponding to 344 nm light) obtained at the Density Functional Theory B3LYP/6-31G(d) level.
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Affiliation(s)
- Shuguang Wang
- Department of Chemistry, Jackson State University, Jackson, MS 39217, USA
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Lysenkov D, Engstler J, Dangwal A, Popp A, Müller G, Schneider JJ, Janardhanan VM, Deutschmann O, Strauch P, Ebert V, Wolfrum J. Nonaligned carbon nanotubes anchored on porous alumina: formation, process modeling, gas-phase analysis, and field-emission properties. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2007; 3:974-85. [PMID: 17514768 DOI: 10.1002/smll.200600595] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
We have developed a chemical vapor deposition (CVD) process for the catalytic growth of carbon nanotubes (CNTs), anchored in a comose-type structure on top of porous alumina substrates. The mass-flow conditions of precursor and carrier gases and temperature distributions in the CVD reactor were studied by transient computational fluid dynamic simulation. Molecular-beam quadrupole mass spectroscopy (MB-QMS) has been used to analyze the gas phase during ferrocene CVD under reaction conditions (1073 K) in the boundary layer near the substrate. Field-emission (FE) properties of the nonaligned CNTs were measured for various coverages and pore diameters of the alumina. Samples with more dense CNT populations provided emitter-number densities up to 48,000 cm(-2) at an electric field of 6 V microm(-1). Samples with fewer but well-anchored CNTs in 22-nm pores yielded the highest current densities. Up to 83 mA cm(-2) at 7 V microm(-1) in dc mode and more than 200 mA cm(-2) at 11 V microm(-1) in pulsed diode operation have been achieved from a cathode size of 24 mm2.
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Affiliation(s)
- Dmitry Lysenkov
- Bergische Universität Wuppertal, Fachbereich C Abt. Physik, 42097 Wuppertal, Germany
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Norinaga K, Deutschmann O. Detailed Kinetic Modeling of Gas-Phase Reactions in the Chemical Vapor Deposition of Carbon from Light Hydrocarbons. Ind Eng Chem Res 2007. [DOI: 10.1021/ie061207p] [Citation(s) in RCA: 130] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Koyo Norinaga
- Institut für Technische Chemie und Polymerchemie, Universität Karlsruhe, Engesserstrasse 20, 76131 Karlsruhe, Germany
| | - Olaf Deutschmann
- Institut für Technische Chemie und Polymerchemie, Universität Karlsruhe, Engesserstrasse 20, 76131 Karlsruhe, Germany
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Gross MD, Vohs JM, Gorte RJ. A study of thermal stability and methane tolerance of Cu-based SOFC anodes with electrodeposited Co. Electrochim Acta 2007. [DOI: 10.1016/j.electacta.2006.08.005] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Randolph KL, Dean AM. Hydrocarbon fuel effects in solid-oxide fuel cell operation: an experimental and modeling study of n-hexane pyrolysis. Phys Chem Chem Phys 2007; 9:4245-58. [PMID: 17687473 DOI: 10.1039/b702860a] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Pyrolysis experiments of n-hexane were performed and the product distribution and fuel consumption were measured as a function of temperature. The experimental temperatures ranged from 550-675 degrees C, with a pressure of approximately 1 atm, and residence times of approximately 5 s. N-Hexane was used as a model compound to represent the linear alkanes that might be found in practical hydrocarbon fuels. Under these conditions, high fuel conversion was observed at the higher temperatures and a wide range of products were formed. The experimental observations were compared to predictions from a plug-flow model using a reaction mechanism consisting of 205 species and 1403 reactions. The hydrogen abstraction and isomerization rate coefficients in this model were based on CBS-QB3 calculations. The only model modification was adjustment of the A-factor of the initiation rates to match conversion at one temperature. This model was able to successfully predict the observed trends in both product selectivities as well as fuel conversion over the temperature range. The mechanism was also used to capture the trends previously observed in n-butane pyrolysis under similar experimental conditions. Significant differences in the sensitivity coefficients for the hexane and butane systems are discussed in terms of the competition between beta-scission and isomerization of the initial radicals formed. The kinetic model predicts that n-hexane will be completely converted within 0.1 s in the higher temperature environment ( approximately 800 degrees C) of the anode channel of a solid-oxide fuel cell (SOFC). This result clearly illustrates the need to explicitly account for gas-phase reactions in SOFC models for those cases where hydrocarbons, especially those larger than methane, are fed directly to an SOFC.
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Affiliation(s)
- Katie L Randolph
- Department of Chemical Engineering, Colorado School of Mines, Golden, CO 80401, USA
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Pomfret MB, Demircan O, Sukeshini AM, Walker RA. Fuel oxidation efficiencies and exhaust composition in solid oxide fuel cells. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2006; 40:5574-9. [PMID: 16999142 DOI: 10.1021/es052448b] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Solid oxide fuel cells (SOFCs) are electrochemical devices that rely on ion migration through a solid-state electrolyte to oxidize fuel and produce electricity. The present study employs Fourier transform infrared spectroscopy to quantify the exhaust of an SOFC operating with fuel flows of methane over Ni/YSZ cermet anodes and butane over Ni/YSZ and Cu/CeO2/YSZ cermet anodes. Data show that hydrocarbon fuels can participate in a variety of different reactions including direct electrochemical oxidation, various reforming processes, and surface-catalyzed carbon deposition. These findings have direct consequences for assessing the environmental impact of SOFCs in terms of the exhaust discharged from devices operating with common hydrocarbon fuel feeds. In the work presented below, a measure of fuel oxidation efficiency is found by comparing the partial pressure of CO2 (P(CO2)) in the SOFC exhaust to the partial pressure of CO (P(CO)). The fuel anode combination with the largest P(CO2)/P(CO) ratio is the C4H10 over Cu/CeO2 combination (0.628 +/- 0.016). The CH4 over Ni cell type has the second highest ratio (0.486 +/- 0.023). The C4H10 over Ni cell type gives a ratio of 0.224 +/- 0.001. Attempts to balance the carbon content of the fuel feed and exhaust lead to predictions of SOFC fuel oxidation mechanisms.
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Affiliation(s)
- Michael B Pomfret
- Department of Chemistry and Biochemistry, University of Maryland, College Park, Maryland 20742, USA
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