摘要
目的通过研究柠檬酸钠对Zn-Ni-Mn合金电沉积行为的影响,明确影响合金电沉积行为的决定性因素,并找出最大电极反应速率对应的柠檬酸钠浓度。方法采用循环伏安法(CV)、旋转圆盘电极(RDE)、电化学阻抗谱(EIS)、计时电流法(CA),对不同柠檬酸钠浓度下Zn-Ni-Mn合金电沉积行为进行研究,采用扫描电镜(SEM)、能谱仪(EDS)对Zn-Ni-Mn合金的表面形貌和成分进行表征。结果 CV分析得出,Zn-Ni-Mn合金的电沉积是一个不可逆过程,当柠檬酸钠浓度为0.6mol/L时,合金共沉积还原峰电位最正(-1.642 V,vs. Ag/Ag+)。RDE分析结果表明,Zn-Ni-Mn的电沉积受动力学和扩散过程混合控制,随着柠檬酸钠浓度的增大,沉积受扩散控制的程度减弱。EIS分析得出,Zn-Ni-Mn合金沉积的电极反应速率由吸附态中间产物造成的弛豫和离子扩散共同决定,当柠檬酸钠浓度为0.6 mol/L时,阻抗谱低频端出现了感抗弧,使极化电阻(Rp)减小并达到最低值(349.68Ω·cm2)。CA分析表明,Zn-Ni-Mn合金的形核速率随柠檬酸钠浓度的增大而降低,成核机理由瞬时成核向连续成核转变。SEM与EDS分析表明,随着柠檬酸钠浓度的增大,合金晶粒尺寸逐渐变大。随着合金中Mn含量的减少,晶粒由胞状转变为多边形状。合金中Zn含量的变化规律与电极反应速率的变化规律相一致。结论电解液中Zn^(2+)的主要存在形式对Zn-Ni-Mn合金的电沉积行为起着决定性作用;当柠檬酸钠浓度为0.6mol/L时,Zn^(2+)主要以[ZnHCit]-的形式存在,其中间产物[ZnHCit^(2-)]ads吸附在阴极表面,大大削弱了浓差极化,电极反应速率最快。
The work aims to determine the decisive factor for influencing the alloy electrodeposition process and find out the concentration of sodium citrate corresponding to maximum electrode reaction rate by investigating the effect of sodium citrate on the electrodeposition behavior of Zn-Ni-Mn alloy. The electrodeposition behavior of Zn-Ni-Mn alloy in bath with different sodium citrate concentration was studied by cyclic voltammetry curve(CV), rotating disk electrode(RDE), electrochemical impedance spectroscopy(EIS) and chronoamperometry(CA). The surface morphology and elemental composition of alloy were characterized by scanning electron microscopy(SEM) and energy spectrum analysis(EDS). The electrodeposition of Zn-Ni-Mn was an irreversible process according to the CV analysis. When concentration of sodium citrate was 0.6 mol/L,co-deposition potential peak was most positive(-1.642 V, vs. Ag/Ag+). It was demonstrated by RDE analysis that electrodeposition of Zn-Ni-Mn alloy was a process controlled by dynamics and diffusion and with sodium citrate concentration increased;the influence of mass transfer on alloy deposition became weakened. The EIS analysis indicated that the rate of electrode reaction was determined by relaxation caused by intermediate adsorbate and diffusion of ions. When sodium citrate concentration was0.6 mol/L, an inductance arc appeared at low frequency, making the polarization resistance(Rp) decrease and reach to the minimum(349.68 Ω·cm2). From CA curves, alloy nucleation rate decreased and the nucleation mechanism changed from instantaneous nucleation to continuous nucleation gradually with sodium citrate concentration increased. SEM and EDS results showed that the grain of Zn-Ni-Mn alloy became coarser with increasing of sodium citrate concentration. Grain developed from the cellular to the polygonal shape with decreasing of Mn content in alloy. The variation regularity of Zn content in the alloy was consistent with the electrode reaction rate. The electrodeposition process of Zn-Ni-Mn is determined by dominant species of Zn2+ in electrolyte. When sodium citrate concentration is 0.6 mol/L, Zn2+ ions mainly exists as [ZnHCit]- complexes in electrolyte. The intermediate product, [ZnHCit2-]ads, can be adsorbed on the surface of cathode, that decreases concentration polarization greatly and obtains the fastest electrode reaction rate.
作者
齐海东
郭昭
卢帅
李运刚
杨海丽
QI Hai-dong;GUO Zhao;LU Shuai;LI Yun-gang;YANG Hai-li(School of Metallurgy and Energy,North China University of Science and Technology,Tangshan 063210,China)
出处
《表面技术》
EI
CAS
CSCD
北大核心
2019年第3期201-210,共10页
Surface Technology
基金
国家自然科学基金资助项目(51474088)~~
关键词
Zn-Ni-Mn合金
柠檬酸钠
电沉积行为
成核机理
吸附
浓差极化
Zn-Ni-Mn alloy
sodium citrate
electrodeposition behavior
nucleation mechanism
adsorption
concentration polarization
