The storage mechanism difference between amorphous and anatase as supercapacitors

Although TiO2 nanotubes is a promising electrode as supercapacitors due to its high energy density, easy synthesis and chemical stability, there are draw backs such as low conductivity and capacitance. Many studies concentrated on improving its electrochemical performance itself but little attention...

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Bibliographic Details
Published in:Green energy & environment 2022-02, Vol.7 (1), p.156-164
Main Authors: Zhang, Wanggang, Liu, Yiming, Song, Zhiyuan, Zhuang, Changwan, Wei, Aili
Format: Article
Language:English
Subjects:
Amorphous
Anatase
Electrochemical hydrogenation
Super capacitor
TiO2 nanotube arrays
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Summary:Although TiO2 nanotubes is a promising electrode as supercapacitors due to its high energy density, easy synthesis and chemical stability, there are draw backs such as low conductivity and capacitance. Many studies concentrated on improving its electrochemical performance itself but little attention was payed to the reason of capacitance differences caused by its different crystal structures. Herein, we prepare amorphous and anatase TiO2 nanotubes and hydrogenated them by a simple electrochemical hydrogenation method to improve their conductivity and capacitance. And then study and compare their morphology and structure differences by SEM, TEM, XRD and BET. The results show that the pore size distribution, internal structure order and internal carrier concentration are the main reasons for their electrochemical performance differences. The microporous structure less than 2 nm in amorphous nanotubes act as a trap of electrolyte ions at current density larger than 0.1 μA cm−2, leading to small charge and discharge capacitance. The long-range ordered crystal structure of anatase is more favorable for the orderly diffusion of carriers, reducing the inelastic scattering of carrier diffusion process and the electron hole-complexing probability, making anatase nanotubes exhibit higher coulomb efficiency and cycle stability than that of amorphous ones. In addition to the crystal differences, the mesopores ～2 nm exist in the amorphous TNAs are the main reason for the electrochemical performance, since at relatively high current density, these mesopores will “block” the transport of the Na+. [Display omitted]
ISSN:2468-0257
2468-0257
DOI:10.1016/j.gee.2020.10.004