Aromatic Ester‐Functionalized Ionic Liquid for Highly Efficient CO<sub>2</sub> Electrochemical Reduction to Oxalic Acid
Yingliang Yang, Hongshuai Gao, Jiaqi Feng, Shaojuan Zeng, Lei Liu, Licheng Liu, Baozeng Ren, Tao Li, Suojiang Zhang, Xiangping Zhang
Abstract
Abstract Electrochemical reduction of CO 2 into valuable chemicals is a significant route to utilize CO 2 resources. Among various electroreduction products, oxalic acid (H 2 C 2 O 4 ) is an important chemical for pharmaceuticals, rare earth extraction, and metal processing. Here, an aprotic aromatic ester‐functionalized ionic liquid (IL), 4‐(methoxycarbonyl) phenol tetraethylammonium ([TEA][4‐MF‐PhO]), was designed as an electrolyte for CO 2 electroreduction into oxalic acid. It exhibited a large oxalic acid partial current density of 9.03 mA cm −2 with a faradaic efficiency (FE) of 86 % at −2.6 V (vs. Ag/Ag + ), and the oxalic acid formation rate was as high as 168.4 μmol cm −2 h −1 , which is the highest reported value to date. Moreover, the results of density functional theory calculations demonstrated that CO 2 was efficiently activated to a −COOH intermediate by bis‐active sites of the aromatic ester anion via the formation of a [4‐MF‐PhO‐COOH] − adduct, which finally dimerized into oxalic acid.