纳米多孔结构镍基复合膜电极的电化学法制备及其电容特性

通过对电沉积法得到的Ni-Cu合金镀层进行电化学去合金化处理, 制备了纳米多孔结构金属镍膜. 采用循环伏安法对多孔金属镍膜在1 mol·L^-1 KOH溶液中进行阳极氧化处理, 获得了纳米多孔结构的镍基复合膜电极. 应用扫描电子显微镜(SEM)、X射线衍射(XRD)、X射线光电子能谱(XPS)和电化学技术对所制备的膜电极的物理性质及赝电容特性进行了表征. SEM、XRD和XPS的测试结果表明, 所制备的纳米多孔结构镍基复合膜由Ni、Ni(OH)₂和NiOOH组成. 电化学实验结果显示, 该复合膜在20 A·g^-1的充放电电流密度下, 给出了578 F·g^-1的初始比电容; 在1000次充放电循环后, 它的比电容值为544 F·g^-1, 电容保持率为94%. 纳米多孔结构有利于KOH电解液的渗透, 从而促进反应物种在电极内部的传输; 纳米多孔的金属镍基体可以提高Ni(OH)₂膜的电子导电性; 纳米大小的Ni(OH)₂颗粒能够缩短质子的固相扩散路径. 上述因素是所制备的纳米多孔结构镍基复合膜电极具有优异赝电容特性的主要原因.

Electrochemical Fabrication and Pseudocapacitive Performance of a Porous Nanostructured Nickel-Based Complex Film Electrode

A porous nickel film was prepared by the selective anodic dissolution of copper from an electrodeposited Ni-Cu alloy film. A porous nanostructured nickel-based complex film electrode was further fabricated by oxidizing the obtained porous nickel film using cyclic voltammetry in 1 mol·L-1 KOH solution. The physical properties and pseudocapacitive performance of the as-prepared film electrodes were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and electrochemical techniques. The results of SEM, XRD, and XPS indicate that the obtained complex film electrode consists of Ni, Ni(OH)2, and NiOOH, and it has a porous nanostructure. The electrochemical experiments revealed that the as-prepared porous nanostructured nickel-based complex film electrode had a specific capacitance of 578 F·g-1 at a current density of 20 A·g-1 at the initial cycle and it gave a specific capacitance of 544 F·g-1 after 1000 cycles with a capacitance retention of 94%. The nanoporous structure enhances the accessibility of the KOH electrolyte and promotes reactive species transport within the electrode. The nanoporous Ni substrate may improve the electronic conductivity of the thin Ni(OH)2 film at its surfaces. The nanosized Ni(OH)2 grains can shorten the proton diffusion pathways in the bulk of the solid nickel hydroxide. These factors are responsible for the superior pseudocapacitive performance of the porous nanostructured nickel-based complex film electrode.