碱性溶液中BH_4^-的电化学氧化机理及伏安法测定

Oxidation Process and Concentration Determination of BH_4^- in Alkaline Solution

对比Na BH4碱性溶液Cu、Ag、Ni、Pt和Au电极的循环伏安特性发现,BH-4在Au电极上活性最强,Pt有一定的活性,而Cu、Ag及Ni几乎没有活性。用三电极体系研究了BH-4在Au电极上的氧化机理,分析了碱性体系中不同浓度Na BH4溶液的线性循环伏安特性,讨论了扫描速度、OH-和B(OH)-4浓度等对BH-4氧化峰电位及峰电流的影响。结果表明,以Au电极为工作电极的峰值电流法是BH-4离子定性和定量检测的一种简单、快速、准确的方法。同时,溶液中较大浓度范围内变化的OH-和B(OH)-4对Na BH4的分析无明显影响。

The electrochemical oxidation of NaBH4 on Au, Pt, Ni, Ag, Cu and Ni electrodes were taken into consideration. The most effective metal for BH4 oxidation was found to be Au. Pt electrodes also showed certain activity while, Ni, Ag and Cu were not effective. Electrochemical oxidation reaction of borohydride is a complicated irreversible oxidation process, the electrochemical oxidation behavior of NaBH4 on Au electrode was analyzed by cyclic vohammetry. The results showed that, the BH4 can be indicated as low as 10-Smol/L,and a linear dependence between the oxidation peak formed by NaBH4 direct oxidation and the concentration of NaBH4 was presented in the concentration range from 1 × 10-4 to 1 × 10-2mol/L, which can used as a quantity electroanalysis method for BH4. The effect of electrode area, concentration of OH - and B （OH） 4 - were taken into consideration, a larger area Au electrode shows more excellent performance in both the accuracy and the detection limit, both the concentration of OH - and B （OH） 4- with little effect on the BH4 quantitative analysis at a certain concentration range. This established electroanalysis method could be used to determine the NaBH4 concentration （especially in the process of electrochemical hydroboration） quickly and with excellent reproducibility and good accuracy.