Controllable CO 2 conversion in high performance proton conducting solid oxide electrolysis cells and the possible mechanisms

Nai Shi, Yun Xie, Daoming Huan, Yi Yang, Shuangshuang Xue, Zeming Qi, Yang Pan, Ranran Peng, Changrong Xia, Yalin Lu

Research output: Contribution to journalArticlepeer-review

10 Citations (Scopus)

Abstract

To solve the increasing greenhouse problem and to achieve sustainable carbon cycling, effective conversion of CO 2 through chemical or electrochemical ways is key. In this study, efficient and controllable conversion of CO 2 mainly to CO and CH 4 has been demonstrated in a proton conducting solid oxide electrolysis cell (P-SOEC) using BaZr 0.8 Y 0.2 O 3-δ (BZY) as the electrolyte and SrEu 2 Fe 1.8 Co 0.2 O 7-δ as the anode, in which an excellent current density of 1.23 A cm -2 at 1.5 V was achieved at 550 °C and 100 hours of smooth operation is demonstrated. Compared with the pure steam electrolysis, impedance spectral investigations indicate that the presence of CO 2 in the cathode actually accelerates the electrode reactions, in contrast with that in a regular O-SOEC. This may be attributed to the higher adsorption of CO 2 and more effective conversion of protons over the BZY electrolyte. With the increase of electrolysis current, formation of both CO and CH 4 are enhanced, contradictory to the deduction based on thermodynamic calculations in which the concentration of CH 4 increases while that of CO reduces. In situ Raman and in situ diffuse reflectance FTIR spectroscopy (in situ DRIFTS) was conducted, and reaction routes for CO 2 were then proposed. Continuously replenished protons, which steadily and efficiently react with CO 3 2- to form-OCO- and finally CO, are suggested to play a critical role in the conversion of CO 2 and the formation of CO in the P-SOEC. Our results shed new light on future effective conversion of CO 2 .

Original languageEnglish
Pages (from-to)4855-4864
Number of pages10
JournalJournal of Materials Chemistry A
Volume7
Issue number9
DOIs
Publication statusPublished - 2019
Externally publishedYes

All Science Journal Classification (ASJC) codes

  • Chemistry(all)
  • Renewable Energy, Sustainability and the Environment
  • Materials Science(all)

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