(617ev) Electrochemical CO2 Reduction in an Oxygen-Ion Conducting Solid Oxide Electrolyzer Cell (SOEC)

Authors: 
Gunduz, S., The Ohio State University
Dogu, D., The Ohio State University
Binkley Meyer, K. E., The Ohio State University
Deka, D. J., The Ohio State University
Co, A., The Ohio State University
Ozkan, U. S., The Ohio State University
It is generally accepted that there is a strong correlation between global CO2 emissions and energy consumption [1]. Due to its increasing levels, conversion of CO2 into valuable products has become an important objective in recent years. High temperature electrolysis of CO2 in the presence of H2O is considered a promising route for syngas (CO+H2) production, which could be used for Fischer-Tropsch synthesis.

Solid oxide electrolyzer cells (SOECs) used in high temperature CO2 electrolysis are basically solid oxide fuel cells (SOFCs) operated in reverse [2]. In the present study, an oxygen-ion conducting electrolyzer type reactor was used for the electrolysis of carbon dioxide into carbon monoxide and oxygen using external electricity. The SOEC reactor used in this study consists of a button cell, i.e., an electrode-electrolyte assembly, and an alumina tube. Yttria-stabilized zirconia (YSZ) disc which has a thickness of 125 µm, La-doped strontium titanate (LST) type perovskite and (La0.8Sr0.2)0.95MnO3-δ (LSM) mixed with YSZ were used as electrolyte, cathode and anode, respectively. The activity and stability of synthesized perovskite was compared with Ni-YSZ type commercially available electrode material. In electrocatalytic CO2 reduction experiments, pure carbon dioxide was flowed to the cathode side and data was collected at a current range of 0-5 mA at 600oC.

The La-doped strontium titanate type perovskite material used in this study was synthesized via modified Pechini method [3]. The characteristics of the synthesized material were investigated using several techniques such as X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), diffuse reflectance infrared spectroscopy (DRIFTS), CO2-TPO (temperature-programmed oxidation with CO2), and electronic conductivity measurements.

Temperature-programmed oxidation (TPO) was performed on post-reaction button cells (both on LST and Ni-YSZ cells) in order to compare the coke deposition on cathode during CO2 reduction.

The aim of this study is to show that high-temperature electrocatalytic CO2 reduction in a SOEC type reactor is a promising, energy efficient alternative for syngas production. The results obtained so far indicated that La-doped strontium titanate perovskite materials can be considered as promising cathodes for CO2 electro-reduction and using perovskites as cathode material can significantly enhance the durability of the system by lowering the coke deposition.

References:

[1] International Energy Outlook 2013, Report # DOE/EIA-0484, 2013; release date: July 25, 2013.

[2] F. Bidrawn, G. Kim, G. Corre, J.T.S. Irvine, J.M. Vohs, R.J. Gorte, Electrochemical and Solid-State Letters 11 (2008) B167-B170.

[3] X. Lu, T.S. Pine, D.R. Mumm, J. Brouwer, Solid State Ionics 178 (2007) 1195.

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