Effect of complexation of cadmium ions with N-methylpyrrolidone on kinetics of their electroreduction in sulfate electrolyte

Calculation of coordination numbers showed that N-methylpyrrolidone (N-MP) forms stable 1: 4 metal-ligand complexes in sulfate cadmium-plating electrolytes. Methods of computer simulation and quantum-chemical calculations allowed establishing that thermodynamically stable Cd(II) complexes formed in the bulk of the sulfate electrolyte contain, apart from four N-MP molecules, four water molecules that provide additional stabilization of the complex due to formation of hydrogen bonds between the ligands. Electrochemical studies indicate the predominant participation of Cd(II) complexes in the electrode reaction. Their discharge is preceded by their slow dissociation. Hindrance of the process of Cd2+ ion electrore-duction from complex electrolytes results in improvement of the structure and quality of cathodic cadmium deposits.