Effect of Applied Voltage on Slow-Release of Cu(II) Ions on the Synthesis of Copper(II) Stearate Complex by Electrochemical Technique

An electrochemical technique based on the slow-release of Cu2+ ion from electrochemical oxidation of a Cu anode in the presence of stearic acid (HSt) and an aqueous solution of ammonium acetate (CH3COONH4) (0.1 mol L-1) as supporting electrolyte has been used to synthesize Cu(II) stearate (Cu(II)St) complex. Different values of applied voltages (1, 5 and 10 V) were used during the synthesis to study the effect of applied voltage on the particle size of the Cu nanoparticles and morphology of the synthesized Cu(II)St complex. By using 1 V of applied voltage, small Cu nanoparticle was produced with an average particle size of 2.49 ± 0.82 nm, followed by 5 V (3.61 ± 1.18 nm) and 10 V (6.64 ± 2.72 nm). Another advantage of using 1 V of the applied voltage is the formation of well-shaped petal-like structures of the Cu(II)St complex compared to the synthesis using 5 V and 10 V which inhibit the formation of well-shaped petal-like structure. This proves that the slow-release electrochemical synthesis using lower value of applied voltage has successfully resulted in the formation of small size Cu nanoparticles.

本研究采用基于硬脂酸（stearic acid, HSt）存在下铜阳极电化学氧化以缓慢释放铜离子（Cu²+）、并以0.1 mol·L⁻¹乙酸铵（ammonium acetate, CH3COONH4）水溶液作为支持电解质（supporting electrolyte）的电化学技术，合成了硬脂酸铜(II)（copper(II) stearate, Cu(II)St）配合物。合成过程中设置了1 V、5 V及10 V三种不同的施加电压（applied voltage），以探究施加电压对铜纳米颗粒（copper nanoparticles）粒径以及所合成硬脂酸铜(II)配合物形貌（morphology）的影响。实验结果显示，当施加电压为1 V时，可制得平均粒径（average particle size）为2.49 ± 0.82 nm的小型铜纳米颗粒；施加电压为5 V时，平均粒径为3.61 ± 1.18 nm；施加电压为10 V时，平均粒径为6.64 ± 2.72 nm。相较于采用5 V与10 V电压合成时会抑制规整花瓣状结构（petal-like structures）的形成，采用1 V施加电压时合成的硬脂酸铜(II)配合物可形成形貌规整的花瓣状结构，这是该合成方法的另一优势。上述结果证实，采用较低施加电压的缓慢释放电化学合成法，可成功制备出粒径更小的铜纳米颗粒。