Isolating the impact of CO concentration in syngas mixtures on SOFC performance via internal reforming and direct oxidation

Ong, Katherine M.; Lee, Won Yong; Hanna, J. C.; Ghoniem, Ahmed F.

doi:10.1016/j.ijhydene.2016.03.107

Cited by 31 publications

(21 citation statements)

References 30 publications

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“…It has been shown that in these conditions the presence of carbon oxides CO 2 and CO do not damage the cell. Indeed, as recently confirmed in , CO seems to act as a real electrochemical reactant, according to reaction (1)…”

Section: Introductionmentioning

confidence: 69%

Electrochemical Study of a SOFC with Various H₂‐CO‐CH₄‐CO₂‐N₂ Gaseous Mixtures

et al. 2017

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This work focuses on the operation of a Ni‐YSZ‐based SOFC fueled with a synthetic mixture of gas with composition similar to that obtained from biomass gasification, i.e., mainly composed of H2, CO and CO2 diluted in N2. Polarization, power versus intensity and electrochemical impedance spectroscopy measurements, both at open circuit voltage (OCV) and under polarization, are performed and compared. Results show that, contrary to what is observed at OCV, under current densities corresponding to standard operating conditions, the electrolyte is responsible for the main part of the resistance of the cell.

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Section: Introductionmentioning

confidence: 69%

Electrochemical Study of a SOFC with Various H₂‐CO‐CH₄‐CO₂‐N₂ Gaseous Mixtures

et al. 2017

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“…20,22,23 Researchers have found that O spillover to CO on nickel is a more likely pathway than CO spillover to YSZ because CO molecules have a strong affinity to nickel sites. [24][25][26] However, most MEA models represent CO electrooxidation as a global reaction rather than implementing the detailed * Electrochemical Society Student Member.…”

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confidence: 99%

“…23 It is a complicated task to model the simultaneous electro-oxidation of H 2 + CO in SOFCs because it requires modeling parallel charge transfer pathways along with internal reforming (e.g. the water-gas-shift reaction).…”

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confidence: 99%

“…23 The first modeling section also describes how both the H and O spillover mechanisms account for the possibility of rate-limiting H 2 and CO adsorption onto nickel at high currents. The validity of this detailed model is then tested by comparing model predictions to experimental polarization data for a wide range of anode Conservation equations.-The equation for mass conservation in the gas-phase of the porous anode is:…”

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confidence: 99%

“…The details of this approach are given in a separate study that isolated the impact of CO electrochemistry on cell operating voltage. 23 First, the reversible cell potential (E rev ) is matched to the experimental reversible cell potential for that anode fuel mixture (E rev,exp ). These experimental cell potentials come directly from the same data sets presented throughout this paper, published by Virkar's group at the University of Utah.…”

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confidence: 99%

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Investigation of a Combined Hydrogen and Oxygen Spillover Mechanism for Syngas Electro-Oxidation on Ni/YSZ

Ong

Hanna

Ghoniem

2016

J. Electrochem. Soc.

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An accurate, comprehensive model for the individual and simultaneous electro-oxidation of H 2 and CO on Ni-YSZ is necessary to predict SOFC performance for a range of gaseous fuels. A mechanism that combines hydrogen (H) spillover to YSZ with oxygen (O) spillover to nickel is implemented in a previously-validated 1D-MEA model with detailed gas-phase transport and surface reforming kinetics in the anode. This model is then successfully fitted to a wide range of experimental polarization data for fuel mixtures. The H and O spillover pathways are then investigated in depth for two anode fuel mixtures: 20% H 2 + 80% N 2 and 20% H 2 + 80% CO. Although these studies confirm that H spillover is typically the dominant source of current, they also show that the current produced by O spillover is non-negligible at higher currents. Furthermore, it is observed that H 2 adsorption to nickel becomes the rate-limiting step at high currents in the hydrogen pathways, while the current produced by O spillover to C O(Ni) is never limited by the rate of CO adsorption. The model is then successfully compared to two independent lower temperature data sets. Together these results demonstrate that it is important to model both spillover pathways on Ni/YSZ and to account for rate-limiting H 2 adsorption at high currents. The thermochemical and electrochemical reaction mechanisms within a SOFC anode are complex, particularly when hydrocarbon species are involved.1-3 Elementary reaction steps are needed to accurately depict gas-phase chemistry, heterogeneous surface reforming, and heterogeneous charge-transfer reactions. Understanding the governing mechanisms for internal reforming and electrochemistry is paramount to optimize anode structure and operating conditions. More specifically, it is critical to identify the correct rate-limiting steps in these elementary mechanisms because those steps control the rate at which the cell can produce current. The elementary electro-oxidation reaction mechanisms for H 2 and CO require special attention because both of these fuels are dominant in practical SOFC fuel streams like reformed natural gas, coal syngas and biogas. 4 A couple of reaction mechanism types have been proposed to represent H 2 electrochemical oxidation at the triple-phase boundary (TPB) of Ni-YSZ: (1) hydrogen spillover and (2) oxygen spillover. Hydrogen (H) spillover mechanisms involve a charge-transfer step where hydrogen spills over from nickel to YSZ to react with oxygen. Oxygen (O) spillover mechanisms, on the other hand, involve a charge-transfer step where oxygen spills over from YSZ to nickel to react with hydrogen. Hydrogen electro-oxidation models typically select only one spillover pathway rather than implementing both the H and O spillover pathways simultaneously. Although a few researchers have used O spillover mechanisms to describe H 2 electro-oxidation, 5,6 the majority have implemented H spillover mechanisms.7-14 A few researchers have compared these two pathways and concluded that H spillover mechanisms are bett...

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Carbon Deposition on the Anode of a Solid Oxide Fuel Cell Fueled by Syngas—A Thermodynamic Analysis

Sarma

Dasappa

2020

Proceedings of the 7th International Conference on Advances in Energy Research

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Isolating the impact of CO concentration in syngas mixtures on SOFC performance via internal reforming and direct oxidation

Cited by 31 publications

References 30 publications

Electrochemical Study of a SOFC with Various H₂‐CO‐CH₄‐CO₂‐N₂ Gaseous Mixtures

Electrochemical Study of a SOFC with Various H₂‐CO‐CH₄‐CO₂‐N₂ Gaseous Mixtures

Investigation of a Combined Hydrogen and Oxygen Spillover Mechanism for Syngas Electro-Oxidation on Ni/YSZ

Carbon Deposition on the Anode of a Solid Oxide Fuel Cell Fueled by Syngas—A Thermodynamic Analysis

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Isolating the impact of CO concentration in syngas mixtures on SOFC performance via internal reforming and direct oxidation

Cited by 31 publications

References 30 publications

Electrochemical Study of a SOFC with Various H2‐CO‐CH4‐CO2‐N2 Gaseous Mixtures

Electrochemical Study of a SOFC with Various H2‐CO‐CH4‐CO2‐N2 Gaseous Mixtures

Investigation of a Combined Hydrogen and Oxygen Spillover Mechanism for Syngas Electro-Oxidation on Ni/YSZ

Carbon Deposition on the Anode of a Solid Oxide Fuel Cell Fueled by Syngas—A Thermodynamic Analysis

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Electrochemical Study of a SOFC with Various H₂‐CO‐CH₄‐CO₂‐N₂ Gaseous Mixtures

Electrochemical Study of a SOFC with Various H₂‐CO‐CH₄‐CO₂‐N₂ Gaseous Mixtures