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

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 (La_0.8Sr_0.2)_0.95MnO_3-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 600^oC.

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.