The Electrochemistry of Ni Pattern Anodes Used as Solid Oxide Fuel Cell Model Electrodes

Bieberle, A.; Meier, Lorenz; Gauckler, Ludwig J.

doi:10.1149/1.1372219

Cited by 305 publications

(339 citation statements)

References 36 publications

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“…Even though this work and the preceding papers are discussing the assumptions used in great detail, our main objection is their assumption that charge transfer (as described by the Butler-Volmer equation) is the only rate limiting step. Furthermore, the model was only used to describe the data of Bieberle et al (19), and the model was only able to describe these data to a limited degree. In spite of this it is claimed that the model proves that the effect of water is a simple effect of the change of electrode potential with the change of P H 2 O .…”

Section: Discussion Of Modelsmentioning

confidence: 99%

A Critical Review of Models of the H2/H2O/Ni/SZ Electrode Kinetics

Mogensen

Høgh²,

Jacobsen

2007

ECS Trans.

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Various models of the H 2 /H 2 O/Ni/SZ (SZ = stabilized zirconia) electrode kinetics have been presented in the literature in order to explain the reported experimental data. However, there has been a strong tendency of using a limited set of data to "verify" a given model, disregarding other data sets, which do not fit the model. We have inspected some models in the literature, and problems (e.g. no quantitative model has explained the large variation in reported values of apparent activation energy of the electrode kinetics) as well as strengths of the models are discussed. We point out experimental findings that a useful model must be able to explain such as difference in sensitivity to poisoning by H 2 S due to differences in the detailed composition of the SZ and large change in apparent activation energy by change in cermet preparation. Finally, we will point out some elements, which seem important for any realistic and useful mathematical model of the H 2 /H 2 O/Ni/SZ electrode.

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Section: Discussion Of Modelsmentioning

confidence: 99%

A Critical Review of Models of the H2/H2O/Ni/SZ Electrode Kinetics

Mogensen

Høgh²,

Jacobsen

2007

ECS Trans.

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“…In most instances a reference electrode is retained as part of the configuration. [4][5][6][7][8][9] In contrast to this trend, Fleig and co-workers [10][11][12][13][14] have adopted a point electrode geometry that is explicitly reference-less. For dense, surface-limited electrodes, the assumption that the point geometry has effectively eliminated the contribution of the counter electrode is likely valid.…”

Section: Introductionmentioning

confidence: 99%

Geometrically asymmetric electrodes for probing electrochemical reaction kinetics: a case study of hydrogen at the Pt–CsH2PO4 interface

Sasaki

Hao

Haile

2009

Phys. Chem. Chem. Phys.

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Electrochemical reactions can exhibit considerable asymmetry, with the polarization behavior of oxidation at a given metal|electrolyte interface differing substantially from that of reduction. The reference-less, microcontact electrode geometry, in which the electrode overpotentials are geometrically constrained to the working electrode (by limiting its area) is experimentally convenient, particularly for fuel cell studies, because the results do not rely on accurate placement of a reference electrode nor must oxidant and reductant gases be sealed off from one another. Here, the conditions under which the critical assumption of this geometry applies-that the overpotential at the large-area counter electrode can be ignored-is numerically assessed. It is found that, for cells of sufficiently large area, the effective radius of the counter electrode (which defines the area through which the majority of the current passes) can be expressed directly as a function of electrolyte thickness and the materials properties, s, the conductivity of the electrolyte, and k, the reaction rate constant for the electrochemical reaction at zero-bias. From this effective radius and the true radius of the working electrode, the fraction of electrode overpotential at the latter, defined as the extent of isolation, can be readily computed. Experimental studies of hydrogen electro-oxidation/proton electro-reduction at the Pt|CsH 2 PO 4 interface using two cells of differing dimensions both validate the computational results and demonstrate that asymmetry in such reactions are readily revealed in the micro-electrode, reference-less geometry. The study furthermore confirms the insensitivity of the results to the precise placement of the working electrode, while indicating the importance of very high isolation values (499%) to ensure that overpotential contributions of the counter electrode do not influence the measurements, particularly as bias is increased.

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“…Therefore, a large TPB length is generally essential for high electrode performance. Several experimental studies demonstrated the inverse proportionality of activation overpotential with respect to the TPB length in standard composite electrodes such as Ni-yttria-stabilized zirconia ͑YSZ͒ anodes 2,3 and ͑La,Sr͒MnO 3 ͑LSM͒-YSZ cathodes. 4,5 A composite electrode is usually composed of an electronic conducting phase, an oxygen-ion conducting phase, and pores for gas transportation.…”

mentioning

confidence: 99%

Enhancement in Three-Phase Boundary of SOFC Electrodes by an Ion Impregnation Method: A Modeling Comparison

Zhu

Ding

Xia

2008

Electrochem. Solid-State Lett.

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A theoretical model is proposed to estimate the length of three-phase boundary ͑TPB͒ of ion-impregnation-derived solid oxide fuel cell ͑SOFC͒ electrodes, which have experimentally shown considerable advantages in performance when compared with standard composite electrodes such as Ni-yttria-stabilized zirconia ͑YSZ͒ and ͑La,Sr͒MnO 3 -YSZ. The electrode is modeled as a spherepacked framework whose surface is coated with second-phase nanoscale particles. Compared with the composite electrodes, the impregnated electrodes show great enhancement in TPB length, theoretically indicating the feasibility of achieving highly electrochemically active electrodes by means of ion impregnation. Solid oxide fuel cells ͑SOFCs͒ are promising to be the nextgeneration energy-conversion devices due to their high efficiency and ultralow pollution emission.1 Many efforts have been made recently to lower their operating temperatures from conventional ϳ1000°C to 600-800°C, in order to significantly reduce the manufacturing cost and improve the stability of the SOFC system. At a reduced operating temperature, the electrode performance becomes the most important determinant of the overall cell output, especially when a thin-film electrolyte ͑i.e., 5-20 m͒ is applied. The electrode performance is believed to be determined by the sum of various polarizations typically associated with the length of the socalled three-phase boundary ͑TPB͒ where the electronic conductor, ionic conductor, and gases are in contact with each other so that the electrochemical reaction can take place. Therefore, a large TPB length is generally essential for high electrode performance. Several experimental studies demonstrated the inverse proportionality of activation overpotential with respect to the TPB length in standard composite electrodes such as Ni-yttria-stabilized zirconia ͑YSZ͒ anodes 2,3 and ͑La,Sr͒MnO 3 ͑LSM͒-YSZ cathodes. 4,5 A composite electrode is usually composed of an electronic conducting phase, an oxygen-ion conducting phase, and pores for gas transportation. Typical examples of the electronic phases are Ni and LSM, which also serve as the electrocatalyst in the anode and cathode, respectively. The ionic phase is generally an electrolyte material such as YSZ and doped ceria ͑DCO͒. The TPB length of such a composite electrode is dominantly affected by its microstructure characteristics including particle size, porosity, and distribution state of the electronic and ionic conducting phases.Various electrode models have been established to predict and improve the performance of the composite electrode with regards to its microstructure parameters.6-8 Tanner et al. 7 developed a model to show the effect of microstructure on the performance of an electrode consisting of a contiguous electrolyte region, a contiguous electrocatalyst, and contiguous porosity. The microstructure is treated as regularly spaced corrugations as shown in Fig. 1a. Their results suggest that the finer the microstructure of the electrode, the higher the electrode performance. A s...

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The Electrochemistry of Ni Pattern Anodes Used as Solid Oxide Fuel Cell Model Electrodes

Cited by 305 publications

References 36 publications

A Critical Review of Models of the H2/H2O/Ni/SZ Electrode Kinetics

A Critical Review of Models of the H2/H2O/Ni/SZ Electrode Kinetics

Geometrically asymmetric electrodes for probing electrochemical reaction kinetics: a case study of hydrogen at the Pt–CsH2PO4 interface

Enhancement in Three-Phase Boundary of SOFC Electrodes by an Ion Impregnation Method: A Modeling Comparison

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