摘要
在电位法、纸上电泳法研究硝酸银-氨-吡啶甲酸体系配合物组成的基础上,采用线性电位扫描、时间电位法、旋转圆盘电极和示踪原子等方法研究了该体系的阴极过程和吡啶甲酸的作用.结果表明,当溶液中硝酸银含量为5×10M,pH=9.2,银(Ⅰ)、氨和吡啶甲酸的摩尔比为1:2.5:5左右时,α-吡啶甲酸体系在一定过电位区,存在混合配体配合物的均相前置转化速率控制步骤,而β(或γ)-吡啶甲酸体系则在相同条件下不存在前置转化速率控制步骤.示踪原子法的研究结果表明,三种吡啶甲酸均在银电极上有不同程度的吸附.在此基础上,分别探讨了电极反应的历程以及吡啶甲酸对电极过程的影响.
The cathodic processes of eletrodeposition of silver in AgNO-NH-pyridinecarboxylic acid systems have been studied by eletrochemical and radiotracer methods.The results of linear potential sweep measurements show that all three isomeric pyridinecarboxylic acids increase the overpotential of the eletrodeposition of silver from AgNO-NHsolution.It has been shown by EMF measurements and paper electrophoresis that in the title systems the AgNO-NH-L(pyridinecarboxylic acid)type mixed ligand complex may be formed under certain conditions.The occurrence of this type of complex depends upon the mole ratio of the silver ion and the ligands.The total concentration of the components in the solution studied in this paper are as follows:C=5×10M,C=2.5×10M,C=2.5×10M,pH=9.2.It was found that in these three cases the main complex was AgNHL inα-pyridine carboxylic acid system and Ag(NH)inβ-orγ-pyridinecarboxylic acid systems.A preceding chemical reaction has been revealed as the rate determining step by chronopotentiometry and rotating disc method inα-pyridinecarboxylic acid system in the high overpotential region but was not observed inβorγ-pyridinecarboxylic acid systems.Results of radiotracer measurements indicate that all isomeric pyridinecarboxylic acids are probably adsorbed on the silver electrode.The increase of the overpotential by addition ofβorγ-pyridinecarboxylic acid was attributed to the adsorption and formation of surface complex on the electrode.
出处
《化学学报》
SCIE
CAS
1985年第2期120-125,共6页
Acta Chimica Sinica
