Ce3+/Ce4+电对在混酸(硫酸和甲磺酸)中的电化学行为

采用循环伏安、线性扫描、交流阻抗等技术研究了Ce³⁺/Ce⁴⁺电对在混酸(硫酸与甲磺酸)中的电化学行为，并对该体系在间接有机电合成中的应用进行了探索.结果表明：当硫酸和甲磺酸(MSA)浓度分别为0.8和1.0 mol·L^-1时，Ce³⁺/Ce⁴⁺电对具有最佳的电化学活性；在上述配比的混酸介质中，铈盐的溶解度得到了大幅提高，同时电解氧化铈(III)离子的电流效率较高（92.1%），与纯硫酸体系中的电流效率接近（92.8%），明显高于纯甲磺酸体系（78.5%）；该混酸介质中Ce⁴⁺在氧化茴香醚生成茴香醛这一过程中也表现出很好的氧化能力.

Electrochemical Behaviors ofCe3+/Ce4+ Couple in a Mixed-Acid Medium of CH3SO3H and H2SO4

In order to determine the optimum molar ratio between methanesulfonic acid (MSA) and sulfuric acid, linear sweep voltammetry (LSV), cyclic voltammetry (CV), and electrochemical impedance spectroscopy (EIS) were used to investigate the electrochemical behaviors of cerium (III)/cerium (IV) (Ce³⁺/Ce⁴⁺couple on a Pt electrode in a mixed acid solution. Various concentrations of sulfuric acid were considered in the experiments, while the concentration of MSA was fixed at 1.0mol·L^-1. It was found that the optimum concentration of sulfuric acid was 0.8mol·L^-1 since the current response was the highest in the control groups and Ce³⁺ was easier to be oxidized toCe⁴⁺. In the mixed acid solution, the solubility of cerium (III) increased to 0.95mol·L^-1 from 0.25mol·L^-1 in 1.3mol·L^-1 sulfuric acid solution. Electrolytic experiment and liquid-phase oxidation had been taken to explore the application of the mixed acid medium. The results revealed thatCe³⁺ exhibited the excellent electrochemical activity andCe⁴⁺demonstrated a stronger oxidation capacity in the mixed acid solution.