Abstract: This study systematically investigates the influence of FeCl2 concentration on the electrochemical behavior of the AlCl3-BMIC (1-butyl-3-methylimidazolium chloride) ionic liquid system, aiming to optimize the electrolyte composition for the controllable electrodeposition of high-iron-content Fe-Al alloys. The variations in ionic conductivity and electrochemical reduction kinetics are analyzed via conductivity measurements and cyclic voltammetry (CV). The results demonstrate that the ionic conductivity of the AlCl3-BMIC-FeCl2 ionic liquid decreases linearly with increasing FeCl2 concentration. This phenomenon is attributed to the reaction between FeCl2 and [Al2Cl7]? to form bulky [Fe(AlCl4)4]2- complexes, which reduces the mobility of charge carriers. In contrast, conductivity exhibits a positive correlation with temperature, following the temperature-dependent Kohlrausch empirical formula. As the concentration increases from 10 mmol/L to 90 mmol/L, the activation energy for ionic migration slightly increases from 9.18 kJ/mol to 9.95 kJ/mol, which originates from the hindrance effect of the generated bulky [Fe(AlCl4)4]2- complex ions on ion transport. Cyclic voltammetry indicate that Fe(II) significantly inhibits the reduction of Al(III). With increasing FeCl2 concentration, the aluminum deposition potential shifts negatively, and the reduction peak current density decreases, this is directly related to the reduced concentration of the electroactive species [Al2Cl7]-. The Fe(II) reduction peak current density increases with FeCl2 concentration while its reduction potential shifts negatively, likely due to decreased activity of [Fe(AlCl4)4]2- ions and enhanced ion-pair interactions. A linear relationship between the Al(III) reduction peak current density and Fe(II) concentration reveals the inhibitory effect of Fe(II) on aluminum electrodeposition. Additionally, the potential difference between Fe(II) and Al(III) reduction gradually decreases with increasing FeCl2 concentration, facilitating the co-deposition of Fe-Al alloys. Based on this trends, Fe-Al alloys with Fe contents ranging from 13.5wt%~68.1wt% are successfully prepared by adjusting the FeCl2 concentration. Their microstructure exhibits a progressive evolution: from nodular aggregates to uniform microspheres and floral structures. These results highlight FeCl2 concentration as a key parameter for tailoring Fe-Al alloy composition and microstructure, enabling controllable synthesis of Fe-rich coatings for advanced applications.

Key words: ionic liquid, ferrous chloride, conductivity, electrochemical performance, electrodeposition

摘要： 本研究系统探究了FeCl2浓度对AlCl3-BMIC离子液体体系电化学行为的影响，旨在通过优化电解液组分，实现高铁含量Fe-Al合金的可控电沉积。通过电导率测试和循环伏安法(CV)分析了离子电导率及电化学还原动力学的变化规律。结果表明，随FeCl2浓度增加，离子液体的电导率呈线性下降趋势，这一现象源于FeCl2与[Al2Cl7]-反应生成大体积的[Fe(AlCl4)4]2-络合物，导致载流子迁移率降低，且电导率随温度的变化符合Kohlrausch经验公式。当FeCl2浓度从10 mmol/L增至90 mmol/L时，离子迁移活化能由9.18 kJ/mol升至9.95 kJ/mol，这源于生成的大体积[Fe(AlCl4)4]2-络合离子对离子传输的阻碍作用。循环伏安测试表明，Fe(II)对Al(III)的还原具有显著抑制作用，随着FeCl2浓度增加，铝沉积电位向负方向偏移，还原峰电流密度降低，这与电活性物质[Al2Cl7]-浓度的降低直接相关；而Al(III)还原峰电流密度与Fe(II)浓度的线性关系揭示了Fe(II)对铝电沉积的抑制作用。此外，Fe(II)与Al(III)还原电位差随FeCl2浓度增加逐渐减小，促进了Fe-Al合金的共沉积。基于上述影响规律，本研究通过调节FeCl2浓度，成功制备出Fe含量为13.5wt%~68.1wt%的Fe-Al合金，其微观结构呈现从结节状聚集体、微球状排列到花状结构的逐步演变特征。

关键词: 离子液体, 氯化亚铁, 电导率, 电化学性能, 电沉积