水溶液中I^-I_2-X^-(X=F、Cl、Br)体系的循环伏安研究

Study on the Aqueous System I^--I_2 -X^- (X=F, C1,Br) by Cyclic Voltammetry

测定了室温下(20±1℃),H_2SO_4水溶液中I^-及I_2分别在F^-、C1^-、Br^-存在时,在Pt电极上的循环伏安图.I^-C1^-及I^-Br^-体系在0.2—1.0V(vs.SCE)范围内,都有两对基本可逆的氧化还原峰.第一对氧化还原峰的位置和峰高不随C1^-或Br^-.的浓度而变化,对应于反应:2I^-(?)I_2+2e;第二对氧化还原峰的位置随Cl^-或Br^-的浓度增加而负移,但峰高不变,浓度增大10倍,峰电势分别负移88±2mV和113±2mV,与由I_2-C1^-及I_2-Br^-体系在0.6-1.0V范围内得到的规律一致,对应的反应分别为I_2C1+3C1^-(?)2C1_2+2e和I_2+4Br_-(?)2IBr_2-+2e.F^-在该电势范围内不参与反应.

The behavior of cyclic voltammetry of systems I- -X- and I2-X- was studied on the stationary plane platinum electrode in an aqueous solution of sulfuric acid of 1 mol·dm-3 at 20±1℃.There are two pairs of fairly reversible redox waves in system 1- -X-(X = C1, Br) between 0.2 and 1.0 V vs. SCE. The peak potentials and peak currents of the first pairs of redox waves in the both systems do not change with the variation of the concentration of C1- and Br-. A tenfold increase of concentration of C1- and Br- causes a shift of the second pairs of redox peak potentials of 88±2mV and 113±2mV towards, less positive values respectively, while the peak currents remain constant. In system I2-X-(X=C1, Br), the same behavior as the second pairs of redox waves in system I- -X- was found.From the experimental results and the approximative treatments of nernstian waves, it can be concluded that the first pairs of redox waves correspond the reaction 2I-(?)I2 + 2e, and the second pairs of redox waves are in agreement with I2C1- + 3C1-(?)2lC1-2 + 2e and I2+ 4 Br-(?) 2 IBr-2 + 2erespectively. F- dose not join the reaction in the given conditions.