【作者】 郑利峰；

【导师】 张九渊； 郑国渠；

【作者基本信息】 浙江工业大学 ， 材料学， 2004， 硕士

【摘要】 与传统的镍电积技术相比，氨络合物体系电积金属镍有着众多的优势和特点。本文在前期工艺研究的基础上着重对氨络合物体系电积金属镍的反应机理、镍在玻璃碳上的电化学成核机理、阳极黑镍的形成机理、阳极析氮过程及Ti基IrO₂涂层阳极对析氮的电催化活性进行了系统研究。 在第三章中首先对氨络合物体系电积金属镍的工艺进行了总结，并通过极化曲线测量，对氨络合物体系中镍阴极电沉积电化学行为进行了研究，系统探讨了溶液中总镍离子浓度、氨水浓度、氯化铵浓度、阴离子及温度等工艺条件对镍阴极还原的影响，而后着重对电积镍的反应机理进行了研究。 稳态极化曲线测定表明在NH₃·H₂O浓度为1.25～2.75mol·L^-1的范围之内，直接在电极上放电的络合离子形式为Ni（NH₃）²⁺。不锈钢电极上电积镍的电化学阻抗行为表明氨络合物体系镍电沉积过程是二次放电过程，中频感抗弧是由于中间吸附产物NiOH_ads的弛豫现象引起，低频容抗弧可能是由于吸附氢原子对镍结晶的阻滞作用引起，依据实验结果提出了氨络合物体系镍电沉积的反应机理和等效电路模型。同时采用稳态技术测定稳态极化曲线，对氨络合物体系阴极电积镍的动力学过程进行了研究。 在第四章中，通过采用循环伏安法和恒电位阶跃法研究了氨络合物体系中镍存玻璃碳上电结晶的初期行为。结果表明，镍在该基体上的沉积没有经历UPD过程，镍的电沉积经历了晶核形成过程，在所研究的外加电位范围内，其电结晶按连续成核和三维生长方式进行，外加电位对晶体生长具有显著的影响。通过分析恒电位暂态曲线，求出镍离子的扩散系数D，以及不同外加电位下的饱和晶核数密度N_sat，探讨了外加电位对成核作用的影响。 在第五章中，通过循环伏安法、恒电流还原法及电化学阻抗谱技术对黑镍的形成过程及反应机理进行了初步研究，并通过X射线衍射技术对黑镍的物相进行了表征。研究结果表明，镍的形成过程首先涉及到一个前置化学步骤，即氨络合物离解出Ni²⁺，Ni²⁺与溶液中的OH^-反应生成Ni（OH）₂颗粒，随后发生Ni（OH）₂颗粒的氧化反应，氧化过程中可能出现γ-NiOOH与水反应自放电生成α-Ni（OH）₂的催化反应过程。黑镍形成过程是一个不可逆反应过程。 黑镍的产物可能包括p一NiooH、丫一iooH，而且还可能包含其它的高价镍化合物，比如Ni3O4，NiZO3，NIOZ等。 阳极反应的电化学阻抗谱表明，氧化电位较低时Ni（OH）:氧化生成黑镍的过程主要受电化学反应所控制，电位较高时，黑镍形成过程主要受电化学反应及扩散混合控制，电位进一步增加，析氮反应占据主导优势，阳极氧化过程仍主要受电化学反应及扩散混合控制。在本章节最后，还通过循环伏安法研究探讨了温度、氯化镍浓度、氨水浓度、氯化按浓度对黑镍生成量的影响。 在第六章中首先通过采用线性扫描技术对氯盐氨络合物体系Ti基RuO:涂层阳极、Ti基Iro:涂层阳极的析氮过程进行了研究，对三种含有不同氧化物涂层电极的析氮电催化性能进行了比较，并结合扫描电镜（sEM）及能谱（EDx）探讨了不同析氮电催化活性的原因。研究结果表明，当电极电位低于11V （vs.sCE）时，Ti基RuO:涂层阳极、Ti基IrO:涂层阳极析气反应主要为析氮反应，氮气的产生主要是由于氨水在电极上发生电化学氧化引起的。Ti基含PdRuTi的I泊:涂层阳极具有最佳的析氮电催化活性，其可能原因是金属元素PdRuTi的存在导致该电极表面特征裂纹最宽且最深，氧化物涂层总析氮面积增多，电催化活性增加C更多还原

【Abstract】 Compared with the traditional nickel electrodeposition techniques, nickel electrodeposition carried out in leaching solution containing ammonia and chloride has great priorities and characteristics. Based on the nickel electrodeposition process, the nickel electrodeposition mechanism, the electrochemical nucleation of nickel on vitreous carbon, the redox process of black nickel formed on anode, the nitrogen evolution on anode and electrocatalytic activity for nitrogen evolution of Ti based IrO2 anodes were investigated systematically.In the third chapter of this thesis, the nickel electrodeposition process in leaching solution containing ammonia and chloride was summarized, and the electrochemical behaviour of nickel electrodeposition in ammonia complex bath was investigated by measuring polarization curves. The effects of total nickel, ammonia, ammonium chloride concentrations in the electrolyte as well as its anion species and temperature were studied systematically. What’s more, the electrodeposition mechanism of nickel in leaching solution containing ammonia and chloride was elucidated emphatically.It is demonstrated by measuring steady state polarization curves that Ni(NH3)2+ is the direct discharge ion within ammonia concentration range from 1.25 to 2.75 mol L-1. The electrochemical impedance spectroscopy of nickel electrodeposition indicates that nickel electrodeposition occurs in two steps, the medium frequency inductive loop is ascribed to the relaxation of the electrode coverage by an adsorbed intermediate such as NiOHads, the low frequency capacitive loop may be due to the inhibition of nickel electrodeposition by adsorbed hydrogen. The mechanism and equivalent circuit of nickel electrodeposition were proposed on the basis of the analysis of electrochemical impedance spectroscopy. Meanwhile, the kinetics law of nickel electrodeposition was investigated by means of steady-state polarizationcurves.In the fourth chapter of this thesis, the initial stages of electrocrystallization of nickel on vitreous carbon from a leaching solution containing ammonia and chloride were illustrated in terms of cyclic voltammetric and chronoamperometric techniques. The results show that the deposition of nickel on the substrate do not undergo UPD process, but undergoes nucleation process. In the experimental conditions, the electrocrystallization of nickel follows the mechanism of three dimensional progressive nucleation and growth. By analyzing of the potentiostatic transients, the diffusion coefficient D of the depositing nickel ions and saturated nucleus number density Nsat were estimated, the effects of applied potential on nucleation and growth ware also discussed.In the fifth chapter of this thesis, the cyclic voltammetry, and galvanostatic reduction and electrochemical impedance spectroscopy techniques were used to investigate the redox process and reaction mechanism of black nickel formed on anode. Moreover, the X-ray diffraction technique was used to examine black nickel species. The results show that the formation process of black nickel is quasi-reversible, it is involved in pre-adsorption transformation process( CE ), ie Ni2 + is dissociated firstly from ammonia complex, and then combines with OH" into Ni(OH)2 particles, which are oxidized on anode. During the anodic process, Ni(OH)2 which on further charge or overcharge forms NiOOH, and NiOOH which on self-discharge with H2O forms a-Ni(OH)2. This reaction process is probably defined as self-catalytic reaction. It is demonstrated by XRD and chemical analysis that high valent compounds such as Ni3O4, NiO2, Ni2O3 besides-NiOOH, y-NiOOH may be formed on electrode surface. The electrochemical impedance spectroscopy of anodic reaction shows that the formation of black nickel was mainly controlled by electrochemical reaction at low anodic potential, and is mainly controlled by electrochemical reaction and diffusion at high anodic potental. With the increasing of anodic potential., the formation of black nickel is still controlled by electrochemical re更多还原