Xing Ji, Liao Maoying, Zhang Chi, Yin Min, Li Dongdong, Song Ye
Key Laboratory of Soft Chemistry and Functional Materials of Education Ministry, Nanjing University of Science and Technology, Nanjing 210094, China.
Phys Chem Chem Phys. 2017 May 31;19(21):14030-14041. doi: 10.1039/c7cp02016c.
To investigate the effect of anions on the electrochemical properties of polyaniline (PANI) for supercapacitors, electrochemical performance tests of PANI with different dopant anions were carried out in the corresponding acid solutions by cyclic voltammetry (CV) and galvanostatic charge-discharge (GCD) methods. In particular, ionic fluxes and solvent molecules involved in redox processes can be analyzed by the electrochemical quartz crystal microbalance (EQCM) technique and discriminated by simultaneously recording cyclic voltammograms and mass changes during redox switching. The emeraldine base (EB) form of PANI prepared in a protonic acid with bigger anions can be easily doped by a protonic acid with smaller anions, and conversely, PANI-EB is hard to be doped. The anodic reversal potential of potentiodynamic cycling heavily influences the electrochemical stability of PANI. High anodic potentials result in PANI degradation. Its supercapacitive properties including specific capacitance, power density and cycling stability are strongly dependent upon the type of dopant anion. PANI with the dopant anions of oxalic acid has the highest specific capacitance and the best cycling stability among the used acids. The diffusion coefficient of anions plays a key role in determining power density. PANI films with organic dopant anions exhibit better cycling stability than their inorganic counterparts. It is believed that the hydrolysis of PANI facilitated by the additional water molecules accompanied by dopant anions into and out of the PANI matrix is a key factor responsible for the cycling instability.
为研究阴离子对用于超级电容器的聚苯胺（PANI）电化学性能的影响，采用循环伏安法（CV）和恒电流充放电（GCD）方法，在相应的酸性溶液中对含不同掺杂剂阴离子的聚苯胺进行了电化学性能测试。特别地，氧化还原过程中涉及的离子通量和溶剂分子可通过电化学石英晶体微天平（EQCM）技术进行分析，并通过同时记录氧化还原切换过程中的循环伏安图和质量变化来加以区分。在含较大阴离子的质子酸中制备的聚苯胺的翡翠碱（EB）形式，可被含较小阴离子的质子酸轻松掺杂，反之，聚苯胺 - EB则难以被掺杂。动电位循环的阳极反向电位对聚苯胺的电化学稳定性有很大影响。高阳极电位会导致聚苯胺降解。其超级电容性能，包括比电容、功率密度和循环稳定性，强烈依赖于掺杂剂阴离子的类型。在所使用的酸中，含草酸掺杂剂阴离子的聚苯胺具有最高的比电容和最佳的循环稳定性。阴离子的扩散系数在决定功率密度方面起着关键作用。含有机掺杂剂阴离子的聚苯胺薄膜比含无机掺杂剂阴离子的薄膜表现出更好的循环稳定性。据信，掺杂剂阴离子进出聚苯胺基质时伴随的额外水分子促进了聚苯胺的水解，这是导致循环不稳定的关键因素。
