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Correlation between hydrogen production rate, current, and electrode overpotential in a solid oxide electrolysis cell with La0.6Sr0.4FeO3-δ thin-film cathode.

Walch G, Opitz AK, Kogler S, Fleig J - Monatsh. Chem. (2014)

Bottom Line: Determination of the current as well as outlet gas composition revealed the electrochemical reduction of some residual oxygen in the cathodic compartment.At 640 °C a water-to-hydrogen conversion rate of ca. 4 % was found at -1.5 V versus a reversible counterelectrode in 1 % oxygen.This causes difficulties in determining the cathodic overpotential of such a cell.

View Article: PubMed Central - PubMed

Affiliation: Institute of Chemical Technologies and Analytics, Vienna University of Technology, Vienna, Austria.

ABSTRACT

Abstract: A solid oxide electrolysis cell (SOEC) with a model-type La0.6Sr0.4FeO3-δ thin-film cathode (working electrode) on an yttria-stabilized zirconia electrolyte and a porous La0.6Sr0.4Co0.2Fe0.8O3-δ counterelectrode was operated in wet argon gas at the cathode. The hydrogen formation rate in the cathode compartment was quantified by mass spectrometry. Determination of the current as well as outlet gas composition revealed the electrochemical reduction of some residual oxygen in the cathodic compartment. Quantitative correlation between gas composition changes and current flow was possible. At 640 °C a water-to-hydrogen conversion rate of ca. 4 % was found at -1.5 V versus a reversible counterelectrode in 1 % oxygen. Onset of hydrogen formation could already be detected at voltages as low as -0.3 V. This reflects a fundamental difference between steam electrolysis and electrolysis of liquid water: substantial hydrogen production in a SOEC is already possible at pressures much below ambient. This causes difficulties in determining the cathodic overpotential of such a cell.

No MeSH data available.


Current–voltage curves calculated from the detected changes of hydrogen () and oxygen concentrations () in the working electrode gas flow. The sum curve (Itot) of these two calculated currents corresponds acceptably well to the measured dc currents (I)
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Fig4: Current–voltage curves calculated from the detected changes of hydrogen () and oxygen concentrations () in the working electrode gas flow. The sum curve (Itot) of these two calculated currents corresponds acceptably well to the measured dc currents (I)

Mentions: For known gas flow rates, the gas concentrations shown in Fig. 3b can be transferred into currents via Faraday’s law. Figure 4 displays the calculated currents reflecting oxygen removal from the counterelectrode compartment (IO2) and hydrogen production therein (IH2). The oxygen current clearly dominates for lower voltages, which is not surprising since the thermodynamic voltage Utd,O2 to be overcome by ULSF is small, being given by4\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$U_{{{\text{td,O}}_{ 2} }} = \frac{RT}{4F}{ \ln }\frac{{p}_{\text{O}_{{ 2 ,\,{\text{WE}}}} }}{{p}_{\text{O}_{{ 2 ,\,{\text{CE}}}} }},$$\end{document}Utd,O2=RT4FlnpO2,WEpO2,CE,Fig. 4


Correlation between hydrogen production rate, current, and electrode overpotential in a solid oxide electrolysis cell with La0.6Sr0.4FeO3-δ thin-film cathode.

Walch G, Opitz AK, Kogler S, Fleig J - Monatsh. Chem. (2014)

Current–voltage curves calculated from the detected changes of hydrogen () and oxygen concentrations () in the working electrode gas flow. The sum curve (Itot) of these two calculated currents corresponds acceptably well to the measured dc currents (I)
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC4495065&req=5

Fig4: Current–voltage curves calculated from the detected changes of hydrogen () and oxygen concentrations () in the working electrode gas flow. The sum curve (Itot) of these two calculated currents corresponds acceptably well to the measured dc currents (I)
Mentions: For known gas flow rates, the gas concentrations shown in Fig. 3b can be transferred into currents via Faraday’s law. Figure 4 displays the calculated currents reflecting oxygen removal from the counterelectrode compartment (IO2) and hydrogen production therein (IH2). The oxygen current clearly dominates for lower voltages, which is not surprising since the thermodynamic voltage Utd,O2 to be overcome by ULSF is small, being given by4\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$U_{{{\text{td,O}}_{ 2} }} = \frac{RT}{4F}{ \ln }\frac{{p}_{\text{O}_{{ 2 ,\,{\text{WE}}}} }}{{p}_{\text{O}_{{ 2 ,\,{\text{CE}}}} }},$$\end{document}Utd,O2=RT4FlnpO2,WEpO2,CE,Fig. 4

Bottom Line: Determination of the current as well as outlet gas composition revealed the electrochemical reduction of some residual oxygen in the cathodic compartment.At 640 °C a water-to-hydrogen conversion rate of ca. 4 % was found at -1.5 V versus a reversible counterelectrode in 1 % oxygen.This causes difficulties in determining the cathodic overpotential of such a cell.

View Article: PubMed Central - PubMed

Affiliation: Institute of Chemical Technologies and Analytics, Vienna University of Technology, Vienna, Austria.

ABSTRACT

Abstract: A solid oxide electrolysis cell (SOEC) with a model-type La0.6Sr0.4FeO3-δ thin-film cathode (working electrode) on an yttria-stabilized zirconia electrolyte and a porous La0.6Sr0.4Co0.2Fe0.8O3-δ counterelectrode was operated in wet argon gas at the cathode. The hydrogen formation rate in the cathode compartment was quantified by mass spectrometry. Determination of the current as well as outlet gas composition revealed the electrochemical reduction of some residual oxygen in the cathodic compartment. Quantitative correlation between gas composition changes and current flow was possible. At 640 °C a water-to-hydrogen conversion rate of ca. 4 % was found at -1.5 V versus a reversible counterelectrode in 1 % oxygen. Onset of hydrogen formation could already be detected at voltages as low as -0.3 V. This reflects a fundamental difference between steam electrolysis and electrolysis of liquid water: substantial hydrogen production in a SOEC is already possible at pressures much below ambient. This causes difficulties in determining the cathodic overpotential of such a cell.

No MeSH data available.