**Fengyang Ju 1, Jinjin Zhang <sup>2</sup> and Weiwei Lu 2,\***


Received: 30 July 2020; Accepted: 23 September 2020; Published: 24 September 2020

**Abstract:** The electrochemical reduction of CO2 is a promising way to recycle it to produce value-added chemicals and fuels. However, the requirement of high overpotential and the low solubility of CO2 in water severely limit their efficient conversion. To overcome these problems, in this work, a new type of electrolyte solution constituted by ionic liquids and propylene carbonate was used as the cathodic solution, to study the conversion of CO2 on an Ag electrode. The linear sweep voltammetry (LSV), Tafel characterization and electrochemical impedance spectroscopy (EIS) were used to study the catalytic effect and the mechanism of ionic liquids in electrochemical reduction of CO2. The LSV and Tafel characterization indicated that the chain length of 1-alkyl-3-methyl imidazolium cation had strong influences on the catalytic performance for CO2 conversion. The EIS analysis showed that the imidazolium cation that absorbed on the Ag electrode surface could stabilize the anion radical (CO2 •−), leading to the enhanced efficiency of CO2 conversion. At last, the catalytic performance was also evaluated, and the results showed that Faradaic efficiency for CO as high as 98.5% and current density of 8.2 mA/cm<sup>2</sup> could be achieved at <sup>−</sup>1.9 V (vs. Fc/Fc+).

**Keywords:** electrochemical reduction of CO2; ionic liquids; propylene carbonate; imidazolium cation
