Sulfur Poisoning of Electrochemical Reformate Conversion on Nickel/Gadolinium-Doped Ceria Electrodes

Riegraf, Matthias; Hoerlein, Michael Philipp; Costa, Rémi; Schiller, Günter; Friedrich, K. Andreas

doi:10.1021/acscatal.7b02177

Cited by 46 publications

(50 citation statements)

References 87 publications

(245 reference statements)

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“…Different possible fuel oxidation mechanisms were extensively discussed in our previous work, and the possibility of competitive pathways at double phase and triple phase boundary was pointed out (12,18,19). Thus, it is possible that the change in hydrogen oxidation mechanism is the reason for the different slopes in Figure 4a.…”

Section: Resultsmentioning

confidence: 84%

Electrochemical Impedance Analysis of Ni/CGO10-Based Electrolyte-Supported Cells

Riegraf¹,

Dierickx²,

Weber³

et al. 2019

ECS Trans.

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To obtain a better understanding of the behavior of Ni/CGO fuel electrodes, this work presents a comprehensive investigation of Ni/CGO10-based electrolyte-supported cells. Commercial Ni/CGO10|CGO10|3YSZ|CGO10|Ni/CGO10-based symmetrical cells were characterized between 550 -975 °C at pH 2 = 0.8 bar and pH 2 O = 0.2 bar and for different H 2 /H 2 O gas mixtures at 550 °C. Small electrode area, thin anodes and large gas flow rates were used to minimize mass transport contributions. The distribution of relaxation times (DRT) is calculated and based on the results, an equivalent circuit model is derived. Electrode process contributions on Ni/CGO were calculated by means of a complex non-linear square fit of the equivalent circuit model to experimental data. One low frequency and one middle frequency electrode process were identified and correlated to a surface and a bulk process, respectively. Apparent activation energy barriers for both processes were derived.

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Section: Resultsmentioning

confidence: 84%

Electrochemical Impedance Analysis of Ni/CGO10-Based Electrolyte-Supported Cells

Riegraf¹,

Dierickx²,

Weber³

et al. 2019

ECS Trans.

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“…Full cells with the same fuel electrode were characterized in detail by means of current-voltage characteristics and electrochemical impedance spectroscopy in our previous publications. 13,18,24 The cell was mounted in a ceramic cell housing as depicted in Figure 2 and contacted with Ni meshes on both sides. 5 As a oneatmosphere setup was employed no sealing between the electrodes was required.…”

Section: Methodsmentioning

confidence: 99%

“…This non-stoichiometry is the reason for the mixed ionic and electronic conductivity (MIEC) properties of CGO at high temperature and reducing atmosphere, [15][16][17] which was suggested to cause its high performance and resistivity against sulfur poisoning and coking. 3,13,[18][19][20] In addition to a low frequency process, a middle frequency process at 10 2 Hz has been observed in impedance spectra as well which was suggested to originate from the oxide ion transport from bulk to surface or across the electrolyte/electrode interface. 21,22 However, a systematic study investigating state-of-the-art Ni/CGO10 symmetrical cells has not been carried out yet.…”

mentioning

confidence: 98%

Electrochemical Impedance Analysis of Symmetrical Ni/Gadolinium-Doped Ceria (CGO10) Electrodes in Electrolyte-Supported Solid Oxide Cells

Riegraf

Costa

Schiller

et al. 2019

J. Electrochem. Soc.

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One of the most powerful tools in solid oxide cell (SOC) characterization is electrochemical impedance spectroscopy, which can unfold important insights into SOC performance characteristics and degradation behavior. To obtain a better understanding of the electrochemical behavior of Ni/CGO fuel electrodes, this work presents a comprehensive investigation of state-of-the-art Ni/CGO10based electrolyte-supported cells. Commercial Ni/CGO10|CGO10|3YSZ|CGO10|Ni/CGO10 symmetrical cells were characterized between 550-975°C at pH 2 = 0.8 bar and pH 2 O = 0.2 bar, and for different H 2 /H 2 O gas mixtures at 550°C. (i) Small electrode area, (ii) thin electrodes and (iii) large gas flow rates were used to minimize mass transport contributions. Based on distribution of relaxation times (DRT) analysis an equivalent circuit model was derived. Electrode process contributions on Ni/CGO were determined by means of a complex non-linear least square fit of the equivalent circuit model to the experimental data. One low frequency process at 0.1-1 Hz and one middle frequency process at 10-100 Hz were identified and correlated to a surface and a bulk process, respectively. Values for the apparent activation energy barriers and reaction orders with respect to steam and hydrogen content were determined.

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“…The setup for cell testing enables the characterization of up to four cells simultaneously and was already illustrated and described in a similar configuration in detail elsewhere. [16,17] Anode and cathode were contacted with nickel and platinum meshes, respectively, and gold was used as the sealant between the anode and the cathode side, thus avoiding the use of silica-containing materials. In all tests, cells were operated at a constant total fuel flow rate of 2 SLPM (standard liter per minute) for each cell.…”

Section: Methodsmentioning

confidence: 99%

A parameter study of solid oxide electrolysis cell degradation: Microstructural changes of the fuel electrode

Hoerlein

Riegraf

Costa

et al. 2018

Electrochimica Acta

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106

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A parameter study of 20 solid oxide electrolysis cells was carried out to systematically investigate long-term degradation each over 1,000 h under variation of temperature, humidity and current density. The influence of operating temperature was investigated between 750 and 850 °C, the humidity ranged from 40 % to 80 % H 2 O, and the current density varied between open circuit voltage (OCV) and 1.5 A•cm-2. The progress of degradation was monitored insitu by electrochemical impedance spectroscopy. Five different contributions to the spectra were identified by calculating the distribution of relaxation times and separated via a complex non-linear square fitting routine. The present work focuses on the degradation of the fuel electrode. From SEM analysis, Ni depletion and an increased pore fraction close to the electrode/electrolyte interface was derived, which is correlated with an increased ohmic resistance of the cells. This unidirectional transport of Ni away from the fuel electrode/electrolyte interface leads to an effective electrolyte extension and is the main source of degradation. Ni depletion is shown to be driven by current density and its extent is shown to be dependent on the complex interplay between the operating parameters current density, anode overpotential, humidity and temperature. It is particularly pronounced for pH 2 O larger than 0.8 atm and temperatures above 800 °C. Furthermore, the fuel electrode electrochemistry also exhibits degradation in the high-frequency region around 10 4 Hz.

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Sulfur Poisoning of Electrochemical Reformate Conversion on Nickel/Gadolinium-Doped Ceria Electrodes

Cited by 46 publications

References 87 publications

Electrochemical Impedance Analysis of Ni/CGO10-Based Electrolyte-Supported Cells

Electrochemical Impedance Analysis of Ni/CGO10-Based Electrolyte-Supported Cells

Electrochemical Impedance Analysis of Symmetrical Ni/Gadolinium-Doped Ceria (CGO10) Electrodes in Electrolyte-Supported Solid Oxide Cells

A parameter study of solid oxide electrolysis cell degradation: Microstructural changes of the fuel electrode

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