In this study, a new CO₂ electroreduction electrolyte system consisting of tetrabutylphosphonium 4-(methoxycarbonyl) phenol ([P₄₄₄₄][4-MF-PhO]) ionic liquid (IL) and acetonitrile (AcN) was designed to produce oxalate, and the electroreduction mechanism was studied. The results show that using the new IL-based electrolyte, the electroreduction system exhibits 93.8% Faradaic efficiency and 12.6 mA cm⁻² partial current density of oxalate at −2.6 V. The formation rate of oxalate is 234.4 μmol cm⁻² h⁻¹, which is better than those reported in the literature. The mechanism study using density functional theory (DFT) calculations reveals that [P₄₄₄₄][4-MF-PhO] can effectively activate CO₂ molecule through ester and phenoxy double active sites. In addition, in the phosphonium-based ionic environment, the potential barriers of the key intermediates *CO₂⁻ and *C₂O₄²⁻ are reduced by the induced electric field, which greatly facilitates the activation and conversion of CO₂ molecule to oxalate.

中文翻译：

---

非质子离子液体作为电解质用于高 CO2 电还原草酸盐

在这项研究中，设计了一种由四丁基鏻4-（甲氧基羰基）苯酚（[P _{4444 ] [4-MF-PhO]）离子液体（IL）和乙腈（AcN）组成的新型CO 2}电还原电解质体系来生产草酸盐，和研究了电还原机理。结果表明，使用新的基于 IL 的电解质，电还原系统在 -2.6 V 下表现出 93.8% 的法拉第效率和 12.6 mA cm ^-2的草酸盐分电流密度。草酸盐的形成速率为 234.4 μmol cm ^-2  h ^-1，这比文献中报道的要好。使用密度泛函理论 (DFT) 计算的机理研究表明 [P ₄₄₄₄ ][4-MF-PhO] 可以有效地激活 CO₂分子通过酯和苯氧基双活性位点。此外，在鏻基离子环境中，关键中间体*CO ₂ ⁻和*C ₂ O ₄ ²⁻的势垒被感应电场降低，极大地促进了CO ₂分子的活化和转化为草酸盐。