Shen, Feng-xia, Jin Shi, Tian-you Chen, Feng Shi, Qing-yuan Li, Jian-zheng Zhen, Yun-fei Li, Yong-nian Dai, Bin Yang, and Tao Qu. Journal of Power Sources 378 (2018): 555-561.
Tetrabutylammonium perchlorate (TBAP) is a commonly used supporting electrolyte in organic electrochemistry, which has many outstanding advantages, such as low cost, easy preparation and wide electrochemical window. Propylene carbonate (PC) is usually used as CO2 absorbent in industry. Therefore, propylene carbonate (PC) / tetrabutylammonium perchlorate (TBAP) was selected as the organic medium for CO2 reduction.
Electrochemical Experiment
All electrochemical tests were carried out in H-type electrolytic cell. The cell is divided into two compartments by proton exchange membrane (Nafion 117). PC/TBAP is used as cathodic electrolyte for CO2 reduction and 0.1 M H2SO4 aqueous solution as anodic electrolyte. Zn, Au and Ag foil (99.99%, 2 × 2 mm2) are used as cathodes. The graphite rod (99.99%, 5 mm diameter) is used as an anode. The cathodic potential is measured relative to the I3-/I- reference electrode, which is formed by immersing platinum wire in 0.1 M PC/TBAP. 0.05 M iodine (I2) and 0.1 M tetrabutylammonium iodide (Bu4NI) were added to the reference solution as redox pairs. Since I2 and I- react according to the ionic reaction (I2 + I- = I3-), the reference solution contains 0.05 M I3- and 0.05 M I-. Salt bridge is used to avoid contamination of cathode electrolyte. The salt bridge and the cathode electrolyte use the same solution, the reference electrode and the salt bridge are sealed at the PTFE interface, and the reference electrode is calibrated with ferrocene as the internal standard. Before electrochemical test, PC/TBAP was used as cathode electrolyte, 30min was purged with Ar, dissolved oxygen was removed, and then CO2 was added to obtain CO2-saturated cathode electrolyte. In the process of electrolysis, H2O is oxidized at the anode, and the protons produced are diffused to the cathode through the proton exchange membrane. In the cathode, CO2 is reduced to CO with the participation of protons. Examples of semi-reactions are as follows:
Anodic reaction: 2 H2O - 4 e- → 4H+ + O2
Cathodic reaction: 2 CO2 + 2H+ + 2 e- → CO + H2O
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