Understanding the electrochemical activation behavior of Co(OH)2 nanotubes during the ion-exchange process. (June 2017)

• Record Type: Journal Article
• Authors: Peng, Lu; Lv, Lin; Wan, Houzhao; Ruan, Yunjun; Ji, Xiao; Liu, Jia; Miao, Ling; Wang, Chundong; Jiang, Jianjun
• Is Part Of: Materials today energy. Volume 4(2017)
• Page Start: 122
• Page End: 131
• Publication Date: 2017-06
• Subjects: Co(OH)2 nanotube -- Ni foam -- Ion-exchange -- Supercapcitors -- Phase transformation; Energy development -- Periodicals; Energy industries -- Periodicals; Power resources -- Periodicals; Energy policy -- Periodicals; Energy development; Energy industries; Energy policy; Power resources; Electronic journals; Periodicals; 621.042
• DOI: 10.1016/j.mtener.2017.04.004
• Languages: English
• ISSNs: 2468-6069

Abstract

Abstract: In this work, a Co(OH)2 nanotube array is grown on Ni foam by an electrochemically induced ion-exchange approach. These arrays can be applied in supercapacitors as electrode materials. In the cyclic voltammetry (CV) charging process, the CO3 2- in Co(CO3 )0.5 (OH)·0.11H2 O is replaced by OH − in the electrolyte, leading to structural transformation from nanowire to nanotube due to Kirkendall effect. Electrochemical tests reveal that the as-prepared Co(OH)2 nanotubes array on Ni foam show low specific capacitance in the initial cycles. After activation of electrode materials, the delivered specific capacitance is significantly increased. X-ray diffraction and Fourier transform infrared techniques (FTIR) are used to study the activation mechanism of the Co(OH)2 nanotube array upon CV cycling. With the continuous cycling, phase transformation occurred, in which synthesized Co(OH)2 bonds are completely converted to CoOOH after 150 cycles. Highlights: Co(OH)2 nanotube arrays were synthesized by electrochemically induced ion-exchange. Nanowire converted to nanotube caused by kirkendall effect during ion-exchange process. Activation mechanism was study to understand the reason of electrochemical performance improvement.