Ce^(3+)/Ce^(4+)电对在混酸(硫酸和甲磺酸)中的电化学行为

Electrochemical Behaviors of Ce^(3+)/Ce^(4+) Couple in a Mixed Acid Medium of CH_3SO_3H and H_2SO_4

采用循环伏安、线性扫描、交流阻抗等技术研究了Ce^(3+)/Ce^(4+)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,Ce^(3+)/Ce^(4+)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Ce^(4+)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.

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 1.0 mol·L-1.It was found that the optimum concentration of sulfuric acid was 0.8 mol·L-1 since the current response was the highest in the control groups and Ce3＋ was easier to be oxidized to Ce4＋.In the mixed acid solution,the solubility of cerium（III） increased to 0.95 mol·L-1 from 0.25 mol·L-1 in 1.3 mol·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 that Ce3＋ exhibited the excellent electrochemical activity and Ce4＋ demonstrated a stronger oxidation capacity in the mixed acid solution.