氨基磺酸体系Co-Ni合金电化学共沉积行为及动力学机理

通过稳态阴极极化和电化学交流阻抗(EIS)等方法，研究了在不同钴镍金属离子比例的氨基磺酸电解液中，Co-Ni合金的电化学共沉积行为。结果表明在氨基磺酸体系中，导致Co-Ni合金异常共沉积行为的原因和在硫酸盐，或氯化物体系中的不同。不是由于Co^2 抑制了Ni的沉积，而是由于NH2SO3^-作为双齿配体形成的异核络合物在电极表面吸附，阻滞了镍离子的还原过程。并且以晶体场理论为基础解释了Co^2 和NH2SO3^-形成的高自旋络合物，比Ni^2 所形成的络合物具有较高的晶体场稳定化能(CFSE)，容易分解。因此吸附在电极表面的氨基磺酸根离子对Co2^2 沉积的阻滞作用小于对Ni2^ 的。这样就导致了在氨基磺酸电解液体系中Co^2 的优先沉积。阳极线性扫描曲线表明．钴镍合金中镍含量越高，沉积层在热力学上越稳定，耐蚀性也越好。同时通过EIS的测试，利用等效电路的分析方法和交流阻抗谱解析理论，提出了氨基磺酸电解液中Co-Ni合金共沉积的动力学机理，较好地解释了实验结果。

Electrochemical Anomalous Codeposition of Co-Ni Alloys from Sulfamate Electrolytes and its Mechanism

The anomalous codeposition behavior of Co-Ni alloys from sulfamate electrolytes containing various Co2+/Ni2+ ratios was investigated by steady polarization curves and electrochemistry impedance spectroscopy (EIS) measurements. It was demonstrated that the electrochemical behavior of Co-Ni alloy deposition from sulfamate electrolytes was different significantly from that of from other electrolytes such as chloride or sulfate solutions. It is believed that the codeposition of CO-Ni alloys is inhibited by the adsorption of heteronuclear complexes on the electrode surface and the complexes are formed by the sulfamate anion as the bidentate ligand. From the standpoint of crystal-field theory, high-spin cobalt complexes with higher energy are less stable than that of nickel. Therefore the inhibition of sulfamate anion to Ni2+ is stronger than that to Co2+ and it cause the preferential reduction of Co2+ from the sulfamate solution. Moreover, accordig to the Nyquist plot, a elecrical equivalent circuits for simulating the EIS of Co-Ni codeposition was composed and the reaction kinetic mechanism of the Co-Ni alloy electrochemical codeposition was studied.