アンモニア添加ピロリン酸銅溶液からの銅の電析機構

抄録

An investigation has been made of the electrodeposition of copper from solutions of Cu(P₂O₇)₂^6- containing small amounts of ammonia. It is found that mixed complex ions, Cu(P₂O₇) (NH₃)^2- and Cu(P₂O₇) (NH₃)₂^2-, are formed at small concentrations in the solution, and hence the possible deposition reactions are:
Cu(P₂O₇)₂^6- Cu(P₂O₇)^2-+P₂O₇^4- Cu(P₂O₇)^2-+2e→Cu+P₂O₇^4- (Main) (1)
Cu(P₂O₇) (NH₃)^2-+2e→Cu+P₂O₇^4-+NH₃ Cu(P₂O₇) (NH₃)₂^2-+2e→Cu+P₂O₇^4-+2NH₃ (Secondary) (2) (2′)
The increase in cathodic current caused by addition of ammonia is attributed to the secondary reactions occuring parallel with the main reaction (1). The partial current of the secondary reactions was measured by using a rotating copper disc electrode and it was found that the current is proportional to the Cu(P₂O₇) (NH₃)^2-ion concentration. This indicates that, of the two secondary reactions, (2) is of much more importance. The mechanism of the reaction (2) is discussed in detail and also compared with the one reported previously for the solutions free from ammonia.