焦磷酸盐溶液中铜电沉积过程 Ⅱ. 用旋转电极的研究

焦磷酸铜络合物还原过程中要经过一价铜这个中间产物在一些文献中都假设过。这个问题不仅是有兴趣的理论问题,而且也很有实际价值。因为在工业电镀中经常出现的所谓“铜粉”,常常影响镀层的质量。简单的Cu~(2+)离子在氧化物溶液中进行阴极还原时,曾经用旋转圆环-圆盘电极(RRDE)的方法实验证实了一价铜中间产物的存在。但是在铜以络离子存在时,尤其是在过剩的焦磷酸离子存在下,使得还原在较负的电位下进行。这时是否有一价铜中间产物,尚未见到RRDE的研究。用RRDE研究络离子还原的工作还很少。可是这一有力方法的应用将会揭示许多一般方

THE ELECTRODE PROCESSES OF COPPER ELECTRODEPOSITION FOR PYROPHOSPHATE SOLUTION II. THE STUDY BY ROTATING ELECTRODE METHOD

Cathodic polarization curves has been measured by means of rotating disc and ring-disc electrodes in cupric pyrophosphate solution. Monovalence pyrophosphoric complex of copper has been detected as intermediate of reduction process. Influence of electrode potential on formation of the intermediate has been observed. By means of rotating disc methode the kinetic current of reduction process has been estamited. It has been found that in more negative potential range contribution of kinetic control yet is appreciable. Based on the polt I_(lim)/ω~(1/2)vs.I_(lim) existence of a preceding chemical process has been evidenced. The following reaction mechanism is proposed[Cu(P_2O_7)_2]~(6-) <=> [Cu(P_2O_7)]~(2-)+P_2O_7~(4-)[Cu(P_2O_7)]~(2-)→[Cu(P_2O_7)]~(3-)→Cu+P_2P_7~(4-)