Phi Thuy-Linh, Nguyen Son Tang, Van Hieu Nguyen, Palomar-Pardavé Manuel, Morales-Gil Perla, Le Manh Tu
Faculty of Materials Science and Engineering, Phenikaa University, Hanoi 12116, Vietnam.
Faculty of Biotechnology, Chemistry and Environmental Engineering, Phenikaa University, Hanoi 12116, Vietnam.
Inorg Chem. 2022 Mar 28;61(12):5099-5111. doi: 10.1021/acs.inorgchem.2c00127. Epub 2022 Mar 15.
This work deals with nickel electronucleation and growth processes onto a glassy carbon electrode from NiCl·6HO dissolved in ethylene glycol (EG) solutions with and without 250 mM NaCl as a supporting electrolyte. The physicochemical properties of EG solutions, namely, viscosity and conductivity, were determined for different Ni(II) concentrations. From cyclic voltammetry, it was found that in the absence of the supporting electrolyte, the cathodic efficiency of Ni electrodeposition is about 88%; however, in the presence of the supporting electrolyte, the cathodic efficiency was reduced to 26% due to water (added along the supporting electrolyte) reduction on the growing surfaces of Ni nuclei. This side reaction produced both H and OH ions. Part of the former was occluded in Ni, and the latter reacted with Ni(II) ions in EG forming passivation products such as Ni(OH). Moreover, it was shown that metallic Ni did not catalyze the EG reduction in this system. From chronoamperometry, it was shown that in the absence of the supporting electrolyte, the amount of Ni electrodeposits, for the same overpotential and time, was higher than in the presence of the supporting electrolyte. The - plots recorded in the latter system, for different Ni(II) concentrations, were analyzed using a model which involves a contribution due to multiple 3D nucleation and diffusion-controlled growth and another related to the simultaneous reduction of water on the Ni nuclei growing surfaces. This model allows not only the quantification of the Ni nucleation kinetic parameters but also the effective deconvolution of the individual contributions to the total current; thus, from the integration of the - plots of these contributions, it was demonstrated that the charge amount of each process depends on the Ni(II) concentration. Scanning electron microscopy, energy-dispersive X-ray spectroscopy, micro-Raman spectroscopy, and X-ray photoelectron spectroscopy revealed the presence of pure Ni nanoparticles electrodeposited on the electrode surface. Moreover, X-ray measurements verified the formation of a high-crystallinity face-centered cubic structure with preferred orientation growth on the ⟨111⟩ direction, which were also corroborated by the magnetic measurement performed in a physical property measurement system.
本工作研究了在含有和不含有250 mM NaCl作为支持电解质的乙二醇（EG）溶液中，溶解的NiCl·6H₂O在玻碳电极上的镍电子成核和生长过程。测定了不同Ni(II)浓度下EG溶液的物理化学性质，即粘度和电导率。通过循环伏安法发现，在没有支持电解质的情况下，镍电沉积的阴极效率约为88%；然而，在有支持电解质的情况下，由于镍核生长表面上水（随支持电解质加入）的还原，阴极效率降至26%。这个副反应产生了H⁺和OH⁻离子。前者部分被包裹在镍中，后者与EG中的Ni(II)离子反应形成钝化产物，如Ni(OH)₂。此外，研究表明金属镍在该体系中不催化EG的还原。通过计时电流法表明，在没有支持电解质的情况下，对于相同的过电位和时间，镍电沉积物的量高于有支持电解质的情况。在后者体系中，针对不同的Ni(II)浓度记录的i-t曲线，使用一个模型进行了分析，该模型涉及由于多个三维成核和扩散控制生长的贡献以及另一个与镍核生长表面上水的同时还原相关的贡献。这个模型不仅允许对镍成核动力学参数进行量化，还能对总电流中各个贡献进行有效的反卷积；因此，通过对这些贡献的i-t曲线进行积分，证明了每个过程的电荷量取决于Ni(II)浓度。扫描电子显微镜、能量色散X射线光谱、显微拉曼光谱和X射线光电子能谱揭示了电极表面电沉积有纯镍纳米颗粒。此外，X射线测量证实形成了具有在⟨111⟩方向上择优取向生长的高结晶度面心立方结构，这也得到了在物理性质测量系统中进行的磁性测量的证实。
