抑氢剂提高Zn-Fe合金电镀电流效率的机理初探  

Mechanism for Increase of Current Density by Hydrogen Inhibitor in Zn-Fe Alloy Electrodeposition

作　　者：彭文杰[1] 王云燕[1] 易卫红 

机构地区：[1]中南大学冶金科学与工程学院,湖南长沙410083 [2]株洲市自来水公司水质监测站,湖南株洲412000

出　　处：《材料保护》2006年第11期1-5,共5页Materials Protection

摘　　要：为了从理论上揭示负二价的硫族化合物抑氢剂提高Zn-Fe合金电镀电流效率的本质,采用电化学方法研究了抑氢剂对锌、铁分电流曲线,电极/溶液界面间双电层微分电容的影响,并运用金属的价电子理论阐述了抑氢剂提高Zn-Fe合金电镀电流效率的机理。结果表明抑氢剂的加入使铁沉积的分电流增加,在阴极电流密度为0.20A/dm2时,铁的分电流增加最大,由0.10A/dm2增至0.14A/dm2。抑氢剂选择性化学吸附于铁电极表面的活性点上,明显降低了电极/溶液界面间的微分电容,当抑氢剂浓度从0增加至20mL/L时,双电层微分电容由20.3μF/cm2很快下降至7.0μF/cm2。抑氢剂中显负电性的元素硫比氢原子提供电子的能力强,与铁共享孤对电子,优先吸附于铁电极表面的活性点上,阻碍氢原子的吸附,提高氢气的析出过电势,从而提高Zn-Fe合金电沉积的阴极电流效率。Zn价电子已满,含有孤对电子的硫族化合物不能在其表面发生化学吸附,故抑氢剂对纯Zn电镀的阴极电流效率影响不大。The effect of sulfide compounds as hydrogen inhibitor on the current efficiency in the electrodeposition of Zn-Fe alloy coating was investigated. Thus the dependence of the partial current for Zn and Fe electrodeposition and of the differential capacitance at electrode/electrolyte interface on the hydrogen inhibitor was explored via electrochemical method. The adsorbing mode of the hydrogen inhibitor was discussed, while the mechanisms for the increase in the current efficiency of Zn-Fe alloy electrodeposition were analyzed with respect to valence electron theory. It was found that the introduction of the hydrogen inhibitor led to increase in the partial current of Fe. Namely, the partial current for Fe increased from 0.10 A/dm 2 to the maximum 0.14 A/dm 2 at a cathodic current dendsity of 0.20 A/dm 2 . At the same time, the differential capacitance at the electrode/electrolyte interface decreased obviously with the introduction of the hydrogen inhibitor, which could be attributed to the selective chemical adsorbing of the hydrogen inhibitor at the active points of Fe electrode. Therefore, the differential capacitance at the electrode/electrolyte interface decreased from 20.3 μF/cm 2 to 7.0 μF/cm 2 , as the concentration of the hydrogen inhibitor increased from 0 to 20 mL/L. It was supposed that S of a large electronegativity in the hydrogen inhibitor was capable of sharing lone-pair electrons with Fe and adsorbing at the active points of the Fe electrode surface, which contributed to inhibiting the adsorption of H atoms and increasing the overpotential of hydrogen separation. Subsequently the cathodic current efficiency for the electrodeposition of Zn-Fe alloy coating was increased. However, the hydrogen inhibitor had little effect on the cathodic current efficiency of Zn electrodeposition, because in this case the S species with lone-pair electrons in the inhibitor was hard to be chemically adsorbed on the surface of Zn with fully-occupied outer valence electron orbit.

关 键 词：Zn—Fe合金电镀 电流效率 抑氢剂 机理 

分 类 号：TQ153.2[化学工程—电化学工业]