Studying the CO–CO2 characteristics of SOFC anodes by means of patterned Ni anodes

Utz, Annika; Leonide, André; Weber, André; Ivers-Tiffée, Ellen

doi:10.1016/j.jpowsour.2010.10.056

Cited by 61 publications

(67 citation statements)

References 32 publications

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“…This suggested that with (50e50 COeCO 2 ) and without (96e4 N 2 eCO 2 ) the addition of CO, and regardless of fuel type, there was one rate determining step (RDS) giving rise to these activation energies. These Ea values are similar to those reported for CO oxidation, in the absence of carbon, on a Ni-YSZ anode (0.85e1.42 eV) [33]. The RDS may be similar/ related to the transfer of adsorbed oxygen to an adsorbed CO moiety on the Ni surface of a Ni-YSZ anode, as this process is reported to have a comparable Ea (123.6 kJ/mol, 1.28 eV) [34].…”

Section: Atmosphere Compositionsupporting

confidence: 85%

Hybrid direct carbon fuel cell anode processes investigated using a 3-electrode half-cell setup

Deleebeeck

Arenillas

Menéndez

2015

International Journal of Hydrogen Energy

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Cyclic voltammetry (CV) Bituminous coal Carbon monoxide Carbon dioxide a b s t r a c t A 3-electrode half-cell setup consisting of a yttria-stabilized zirconia (YSZ) electrolyte support was employed to investigate the chemical and electrochemical processes occurring in the vicinity of a model hybrid direct carbon fuel cell (HDCFC) anode (Ni-YSZ) in contact with a molten carbon-alkali carbonate slurry. Electrochemical testing, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), with and without the Ni-YSZ layer highlighted the promotional effect of the Ni-YSZ anode layer, and revealed the contributions of Ni/NiO, and potentially K/K 2 O, redox couple(s). Treated anthracite and bituminous coals, as well as carbon black, were tested, revealing similar open circuit potential and activation energies in mixed 96e4 vol% N 2 eCO 2 and 50e50 vol% COeCO 2 environments between 700 and 800 C. Bituminous coal showed the highest activity, likely associated to a high O/C ratio and hydrogen content. Based on acquired data, a reaction scheme was proposed for processes at the working electrode, including the role of bubble formation in the vicinity of the electrochemically active solid/molten medium interface.

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Section: Atmosphere Compositionsupporting

confidence: 85%

Hybrid direct carbon fuel cell anode processes investigated using a 3-electrode half-cell setup

Deleebeeck

Arenillas

Menéndez

2015

International Journal of Hydrogen Energy

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“…These ratios are in a similar range to those previously reported for various Ni/SZ electrodes. 23 Here we address the reasons for the large differences in relative activity.…”

Section: Resultsmentioning

confidence: 98%

“…15,16 Acceptor-doped ceria is a well-known MIEC solid when exposed to a reducing environment and it exhibits high activity for the H 2 /H 2 O reaction when applied as an electrode. [17][18][19][20] Considerable effort has gone into understanding and modelling the reaction kinetics and mechanisms for the H 2 /H 2 O and CO/CO 2 reactions, especially for Ni-SZ electrodes, [21][22][23][24][25] but also more recently for ceria-based electrodes. 16,[26][27][28] However, relative activities for the CO/CO 2 and H 2 /H 2 O reactions are not well studied, even for conventional Ni-SZ electrodes.…”

Section: -14mentioning

confidence: 99%

Kinetics of CO/CO₂ and H₂/H₂O reactions at Ni-based and ceria-based solid-oxide-cell electrodes

2015

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Document Version Peer reviewed version Link back to DTU Orbit Citation (APA):Graves, C. R., Chatzichristodoulou, C., & Mogensen, M. B. (2015). Kinetics of CO/CO2 and H2/H2O reactions at Ni-based and ceria-based solid-oxide-cell electrodes. Faraday Discussions, 182, Comparing model and porous Ni-SZ electrodes, the ratio of electrode polarization resistance in CO/CO 2 vs. H 2 /H 2 O decreases from 33 to 2. Experiments and modelling suggest that the ratio decreases due to a lower concentration of impurities blocking the three phase boundary and due to the nature of the reaction zone extension into the porous electrode thickness. Besides showing higher activity for H 2 /H 2 O reactions than CO/CO 2 reactions, the Ni/SZ interface is more active for oxidation than reduction. On the other hand, we find the opposite behaviour in both cases for CGOn/STN model electrodes, reporting for the first time a higher electrocatalytic activity of CGO nanoparticles for CO/CO 2 than for H 2 /H 2 O reactions in the absence of gas diffusion limitations. We propose that enhanced surface reduction at the CGOn/gas two phase boundary in CO/CO 2 and in cathodic polarization can explain why the highest reaction rate is obtained for CO 2 electrolysis. For all materials investigated, large differences

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“…Conventional Ni/YSZ cermet anodes act as a catalyst converting hydrocarbon fuels and steam into hydrogen and carbon monoxide [1] and as an electrocatalyst preferentially electro-oxidizing the hydrogen in the reformate. Even though carbon monoxide can be electro-oxidized as well and a stable operation in appropriate CO/CO 2 -mixtures is possible [2][3][4], in reformate-fuelled anode supported cells only H 2 is electro-oxidized at the triple phase boundaries. This is related to the fast catalytic watergas shift reaction on the Ni-surface in the substrate and the anode functional layer of an anode supported cell (ASC) [5].…”

Section: Introductionmentioning

confidence: 99%

Sulfur Poisoning of Anode‐Supported SOFCs under Reformate Operation

et al. 2013

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The impact of sulfur‐poisoning on reforming chemistry and electrochemistry of anode‐supported solid oxide fuel cells is analyzed via electrochemical impedance spectroscopy. Different types of anode supported cells are operated in hydrogen/steam – as well as simulated reformate – (H2 + H2O + CO + CO2 + N2) fuels containing 0.1–15 ppm of H2S. A detailed analysis of impedance spectra by the distribution of relaxation times (DRT) and a subsequent complex nonlinear least squares (CLNS) fit separates the impedance changes taking place at the anode and the cathode. Two main features were detected in the DRT, a decreased reaction rate of the electrochemical hydrogen oxidation and a deactivation of the catalytic conversion of CO via the water‐gas shift reaction. During the first exposure of the cell to a H2S‐containing fuel, an enhanced degradation is observed. The degradation rate increases several hours after H2S was added to the fuel and decreases after the poisoning is completed. The polarization resistance increased by a factor of 2–10, depending on H2S‐content, fuel composition and cell type. Comparing the temporal characteristics of the polarization resistance of two different anode supported cells, it could be shown that the accumulated H2S‐amount divided by the Ni‐surface area inside the anode substrate and anode functional layer determine the onset of the degradation.

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Studying the CO–CO2 characteristics of SOFC anodes by means of patterned Ni anodes

Cited by 61 publications

References 32 publications

Hybrid direct carbon fuel cell anode processes investigated using a 3-electrode half-cell setup

Hybrid direct carbon fuel cell anode processes investigated using a 3-electrode half-cell setup

Kinetics of CO/CO₂ and H₂/H₂O reactions at Ni-based and ceria-based solid-oxide-cell electrodes

Sulfur Poisoning of Anode‐Supported SOFCs under Reformate Operation

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