Fundamentals of electro- and thermochemistry in the anode of solid-oxide fuel cells with hydrocarbon and syngas fuels

Hanna, J. C.; Lee, W.Y.; Shi, Yixiang; Ghoniem, Ahmed F.

doi:10.1016/j.pecs.2013.10.001

Cited by 180 publications

(117 citation statements)

References 173 publications

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“…The accumulation of impurities is one of the main sources of degradation, and it can be reversible or irreversible. Impurities that gradually accumulate at the electrode/electrolyte interface reduce, in fact, the electrochemical activity by blocking the reaction sites of the 1) The critical conditions for carbon deposition depend on the type of carbon-containing species in the fuel and on the carbon formation pathway [17]; a low steam-to-carbon ratio, typically lower than 2, is the common condition that promotes the formation of solid carbon in SOFCs.…”

Section: Introductionmentioning

confidence: 99%

“…In fact, Ni has proven to exhibit a very high catalytic activity toward the carbon deposition reactions in the operating temperature range of SOFCs. An overview on solid carbon formation in SOFC anodes by thermochemical reactions is provided in the work of Hanna et al [17]. Haga et al [9] have first studied the impact of siloxanes on the Ni-anode, showing fast degradation due to silica deposition.…”

Section: Introductionmentioning

confidence: 99%

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Reporting Degradation from Different Fuel Contaminants in Ni‐anode SOFCs

et al. 2017

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The real-life operation of solid oxide fuel cell (SOFC) system has to deal with fuel contaminants which might reduce even significantly the lifetime of reformer and stack depending on the type and amount of contaminant present in the feed stream. From a system perspective, detecting and correlating observed stack and reformer performance degradation with fuel contamination is fundamental to implement correctional procedures (e.g., change of clean-up vessels catalysts) and/or trigger alarms to prevent a further contamination of the fuel cell. In this work, based on own experiments with several fuel contaminants (H 2 S, HCl, tars, siloxanes), we have developed empirical degradation models which are able to quantitatively correlate the range of degradation rate resulting from known amounts of a certain contaminant type in the fuel stream. Degradation induced by carbon deposition is also assessed using a simulation model. The techno-economic trade-off of having ultra-stringent purification requirements on the fuel clean-up unit due to additional operating costs (e.g., for frequent catalysts change) or capital costs (e.g., for vessel over-sizing to accommodate a larger amount of catalysts and possibly of different types) versus the lifetime of the fuel cell stacks is eventually analyzed.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Reporting Degradation from Different Fuel Contaminants in Ni‐anode SOFCs

et al. 2017

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“…In a comprehensive review, Gohniem and coworkers [10] have recently addressed the chemistry of the electro-oxidation of H 2 and CO, both individually and in the case of syngas mixtures: in Ni-YSZ anodes, the electrochemical conversion of syngas is governed by the H 2 electro-oxidation, with the WGS reaction being responsible for the conversion of CO to H 2 O and H 2 , for further electrochemical consumption. H 2 is the dominant electroactive species, whereas CO is not directly electro-oxidized: since the electro-oxidation kinetics of H 2 are much faster than the electro-oxidation kinetics of CO (up to one order of magnitude), H 2 remains the favored electroactive species even when the excess of CO is significant [11].…”

Section: Introductionmentioning

confidence: 99%

Experimental and model analysis of the co-oxidative behavior of syngas feed in an Intermediate Temperature Solid Oxide Fuel Cell

Donazzi

Rahmanipour

Maestri

et al. 2016

Journal of Power Sources

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-SOFCs). The activation of a co-oxidative route is a most distinguishing feature of Ce-based cells, compared to traditional SOFCs. SDC electrolyte supported ITSOFCs with Cu-Pd-CZ80 composite anodes and LSCF cathodes were tested under a wide range of operating conditions. Polarization and EIS measurements were collected at 600°C and 650°C with syngas mixtures (between 2.3 to 0.4 H2/CO ratio), H2/N2 mixtures (from 97 to 30% H2 v/v) and CO/CO2 mixtures (from 97 to 50% CO v/v). A 1D, dynamic and heterogeneous model of the cell was applied to analyze the polarization and the EIS curves. The kinetics of the reactions of H2 electrooxidation, CO electro-oxidation and O2 reduction were individually investigated and global power law rates were derived. The syngas experiments were simulated on a fully predictive basis and no parameter adjustment, confirming that the polarization behavior could be best reproduced exclusively by assuming the presence of the co-oxidative route. The IT-SOFCs were also exposed to biogas mixtures, revealing that the dry-reforming reaction was active. Milan, August 7 th 2015Dear Editor of the Journal of Power Sources, Please find attached our manuscript, entitled "Experimental and model analysis of the cooxidative behavior of syngas feed in an IT-SOFC" by Alessandro Donazzi, Morteza Rahmanipour, Matteo Maestri, Gianpiero Groppi, Luca Bardini, Alfonsina Pappacena and Marta Boaro, which we would like to submit for publication.In this paper, we present experimental and modeling results concerning the activation of a co-oxidative reaction mechanism in IT-SOFCs exposed to syngas mixtures. Novel, Ni-free, Ce-based IT-SOFCs are tested in a wide range of operative conditions, including biogas, syngas, H 2 /N 2 and CO/CO 2 mixtures. By means of model analysis, we show that the electro-oxidation of H 2 and the electro-oxidation of CO are active in parallel when syngas is fed to the cell, that is, the cell is able to directly oxidize CO in addition to H 2 . This is a most significant and promising result, associated to the presence of Ce in the anode formulation. For the first time in the case of ITSOFCs, the co-oxidative mechanism is numerically demonstrated. To accomplish this task, a onedimensional, dynamic and heterogeneous model is presented, which allows to predict both the polarization curves and the impedance spectroscopy curves. The model is based on fundamental conservation equations and also accounts for the presence of parasitic leakage currents, which characterize the behavior Ce electrolytes. A kinetic analysis is performed and power law rates are extracted for the electrocatalytic processes that are active in the cell.The work has not been previously submitted to the Journal of Power Sources, it has not been published previously in any form and is not under consideration for publication elsewhere. All the authors and the host authorities approve the manuscript.Thank you for your kind consideration. power law rates were derived. The syngas experiments were simulated on a fully predictive bas...

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“…The development of kinetic models for surface reactions, charge transfer reactions, and biological reactions is particularly challenging, because there is typically little understanding about the operating reaction pathways and often no knowledge about rate parameter values in these settings. For instance, there exist a number of competing hypotheses about H 2 and CO oxidation mechanisms for a solid-oxide fuel cell (Hanna et al, 2014). The standard approach to building models in such a case is to postulate reaction models and to compare them based on their ability to reproduce indirect system-level experimental data.…”

Section: Introductionmentioning

confidence: 99%

“…The standard approach to building models in such a case is to postulate reaction models and to compare them based on their ability to reproduce indirect system-level experimental data. Data-driven model comparison thus involves defining a metric of fit, e.g., the sum of squared residuals, and selecting a model that minimizes this metric, e.g., least-squares or regularized least-squares fitting (Hanna et al, 2014;Vogler et al, 2009;Yurkiv et al, 2011). The principal limitation of the least-squares fitting approach is that it only identifies a single "best" model and yields point estimates of the underlying parameter values, without providing a meaningful description of the uncertainty among competing models and in their parameters.…”

Section: Introductionmentioning

confidence: 99%

Bayesian inference of chemical kinetic models from proposed reactions

Galagali

Marzouk

2015

Chemical Engineering Science

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Bayesian inference provides a natural framework for combining experimental data with prior knowledge to develop chemical kinetic models and quantify the associated uncertainties, not only in parameter values but also in model structure. Most existing applications of Bayesian model selection methods to chemical kinetics have been limited to comparisons among a small set of models, however. The significant computational cost of evaluating posterior model probabilities renders traditional Bayesian methods infeasible when the model space becomes large. We present a new framework for tractable Bayesian model inference and uncertainty quantification using a large number of systematically generated model hypotheses. The approach involves imposing point-mass mixture priors over rate constants and exploring the resulting posterior distribution using an adaptive Markov chain Monte Carlo method. The posterior samples are used to identify plausible models, to quantify rate constant uncertainties, and to extract key diagnostic information about model structuresuch as the reactions and operating pathways most strongly supported by the data. We provide numerical demonstrations of the proposed framework by inferring kinetic models for catalytic steam and dry reforming of methane using available experimental data.

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Fundamentals of electro- and thermochemistry in the anode of solid-oxide fuel cells with hydrocarbon and syngas fuels

Cited by 180 publications

References 173 publications

Reporting Degradation from Different Fuel Contaminants in Ni‐anode SOFCs

Reporting Degradation from Different Fuel Contaminants in Ni‐anode SOFCs

Experimental and model analysis of the co-oxidative behavior of syngas feed in an Intermediate Temperature Solid Oxide Fuel Cell

Bayesian inference of chemical kinetic models from proposed reactions

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