Chinese Journal of Catalysis ›› 2016, Vol. 37 ›› Issue (7): 1081-1088.DOI: 10.1016/S1872-2067(15)61048-8

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Electrochemical CO2 reduction to formic acid on crystalline SnO2 nanosphere catalyst with high selectivity and stability

Yishu Fua, Yanan Lia, Xia Zhanga, Yuyu liub,c, Xiaodong Zhoud, Jinli Qiaoa   

  1. a. College of Environmental Science and Engineering, Donghua University, Shanghai 201620, China;
    b. College of Environmental Science and Engineering, Taiyuan University of Technology, Taiyuan 030024, Shanxi, China;
    c. Graduate School of Environmental Studies, Tohoku University, Sendai 980-8579, Japan;
    d. Department of Chemical Engineering, University of South Carolina, Columbia, SC 29208, USA
  • Received:2015-12-18 Revised:2016-01-27 Online:2016-06-17 Published:2016-06-17
  • Contact: Yuyu liu, Jinli Qiao
  • Supported by:

    This work was supported by the Innovation Program of the Shanghai Municipal Education Commission (14ZZ074), the International Academic Cooperation and Exchange Program of Shanghai Science and Technology Committee (14520721900), Graduate Innovation Fund of Donghua University (15D311304) and the College of Environmental Science and Engineering, State Environmental Protection Engineering Center for Pollution Treatment and Control in Textile Industry, Donghua University. All the financial supports are gratefully acknowledged.

Abstract:

A novel catalyst for CO2 electroreduction based on nanostructured SnO2 was synthesized using a facile hydrothermal self-assembly method. The electrochemical activity showed that the catalyst gave outstanding catalytic activity and selectivity in CO2 electroreduction. The catalytic activity and formate selectivity depended strongly on the electrolyte conditions. A high faradaic efficiency, i.e., 56%, was achieved for formate formation in KHCO3 (0.5 mol/L). This is attributed to control of formate production by mass and charge transfer processes. Electrolysis experiments using SnO2-50/GDE (an SnO2-based gas-diffusion electrode, where 50 indicates the 50% ethanol content of the electrolyte) as the catalyst, showed that the electrolyte pH also affected CO2 reduction. The optimum electrolyte pH for obtaining a high faradaic efficiency for formate production was 8.3. This is mainly because a neutral or mildly alkaline environment maintains the oxide stability. The faradaic efficiency for formate production declined with time. X-ray photoelectron spectroscopy showed that this is the result of deposition of trace amounts of fluoride ions on the SnO2-50/GDE surface, which hinders reduction of CO2 to formate.

Key words: Carbon dioxide reduction, Tin dioxide, Formate, Faradaic efficiency