Electrochemical CO2 reduction on EC Tag (Cu) Supported Carbon Electrode
Authors: Kawano Asuka , Takatsuji Yoshiyuki , Haruyama Tetsuya 
Published: February 2020

Increase in greenhouse gases, such as carbon dioxide is global issue on the warming of our planet. CO2 reduction is an approach to solving the issue, and studied with various methodologies. We have developed an electrochemical method with metal supported carbon electrodes. Catalytic metal supported electrode could reduce CO2 into valuable substances, such as CO, CH4, C2H6, C2H4, CH3OH, C2H5OH, HCOOH, and etc. Electrochemical CO2 reduction is the one of the efficient chemical process. But both efficiency and reduced products of CO2electrochemical reduction are very much depended on a supported material and its state of support on an electrode.

We have developed EC tag method in order to electrochemical support a catalytic nano metal on economical non-catalytic electrode, such as carbon. EC tag method is our originated method to support metal-peptidic tag complex on solid surface electrochemically [1-3]. EC tag method has been employed to support metal on carbon electrode electrochemically. EC tag method is an unique method to electrical deposition of metal. EC tag-metal complex can be supported through electrochemical reduction. In the EC tag method Cu support, the deposited Cu doesn’t growth much because the metal crystal growth is affected with complexed EC tag. So that means that the EC tag (Cu) can be support in nano size metal on glassy carbon. The supported metal (Cu) shows catalytic activity on CO2reduction and electrolysis of water. We assumed that EC tag method could support nano metal on electrode, so reaction efficiency and product selectivity improved. Therefore, in this study, the supported metal (Cu) was employed EC tag method.

We have objective to clarify alternation of CO2reduction products with the carbon electrode with different condition of metal support.

Electrochemical support of EC tag (Cu) on glassy carbon has been done as follow; electrochemical supporting reaction mixture was containing EC tag (Cu2+) (0.1mM) and KNO3 (0.1mM) and was adjusted of several different pH. Electrochemical EC tag (Cu) supporting was performed in three-electrode system (WE: glassy carbon electrode, CE: Pt electrode, RE: Ag/AgCl electrode) with constant potential application at -200mV, -400mV, or -600mV for max, 30min. Electrochemical reduction of CO2 was performed with the EC tag (Cu) supported glassy carbon electrodes. The CO2 reduction had been done with three electrode system with -600mV constant potential application. CO2 reduced products were changed depending on the pH of EC tag (Cu) supporting reaction mixture. The reaction time length of EC tag (Cu) and Cu supporting have also effect on the CO2reduction products which were vary. These observations suggest that the state of supported EC tag (Cu) is different among the condition of supporting reaction, e.g. pH, supporting potential. We are starting to observe EC tag (Cu)/glassy carbon electrode by atomic force microscopy (AFM) and scanning electron microscope.

In our current results, methane and ethylene was produced by electrochemical CO2 reduction by EC tag (Cu)/glassy carbon electrode which was prepared through specific condition. EC tag metal support modified carbon electrode shows a typical catalytic action in electrochemical CO2 reduction. It suggests potential to apply the EC tag metal support modified carbon electrode for CO2conversion.

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[2] H. Sakamoto and T. Haruyama et al., Analytica Chimica Acta,
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[3] H. Sakamoto and T. Haruyama, Colloids and Surfaces B: 79, 83-87 (2010)