Electrochemical lithium intercalation at single-wall carbon nanotubes chemically attached to 4-aminothiophenol modified platinum electrodes Belinda I. Rosario-Castro a , Enid J. Contés-de Jesús a , Marisabel Lebrón-Colón b , Michael A. Meador b , Ileana González-González a , Carlos R. Cabrera a,⇑ a Department of Chemistry and NASA-URC Center for Advanced Nanoscale Materials, University of Puerto Rico, Río Piedras Campus, PO Box 23346, San Juan, PR 00931-3346, United States b NASA John H. Glenn Research Center, 21000 Brookpark Road, Cleveland, OH 44135, United States article info Article history: Received 29 March 2013 Received in revised form 9 June 2013 Accepted 17 June 2013 Available online 27 June 2013 Keywords: 4-Aminothiophenol Platinum electrodes Lithium intercalation Single wall carbon nanotubes abstract The electrochemical intercalation of lithium has been studied by cyclic voltammetry experiments at sin- gle wall carbon nanotubes (SWCNTs) chemically attached at Pt electrodes with 4-aminothiophenol (4ATP). Cyclic voltammetric studies of Li+ at SWCNT/4ATP/Pt electrodes were done evaluate the revers- ibility of Li intercalation. High-resolution X-ray photoelectron spectroscopy, X-ray diffraction, scanning electron microscopy, and reflection–absorption infrared spectroscopy were done to characterize the structural changes of SWCNTs/4-ATP/Pt electrodes upon electrochemical lithium intercalation. The reversible energy capacity obtained from charge/discharge studies showed a change from 538 mAh/g at the first charge/discharge cycle to 703 mAh/g, at the fifth cycle. The calculated Li storage capacity for SWCNTs/4-ATP/Pt electrodes almost doubled the theoretical capacity for Li intercalation in graphite electrodes. Ó 2013 Published by Elsevier B.V. 1. Introduction The basic working mechanism of rechargeable lithium batteries is associated with electrochemical intercalation and de-intercala- tion of lithium between two working electrodes. Currently, transi- tion metal oxides and carbon materials (graphite or disorder carbon) are being used as the cathodes and the anodes for lithium batteries, respectively [1,2]. It is desirable to have batteries with a high energy density capacity, fast charging time and long cycle life- times. The energy density capacity is determined by the saturation lithium concentration of the electrode materials. For graphite, the thermodynamic equilibrium saturation concentration is LiC 6 , which is equivalent to 372 mAh/g [3]. It has been indicated that a higher Li capacity may be obtained in carbon nanotubes if all the interstitial sites (inter-shell van der Waals spaces, inter-tube channels, and inner cores) are accessible for Li intercalation. Elec- trochemical intercalation at multiwall carbon nanotubes (MWNTs) [4–7] and single wall carbon nanotubes (SWCNTs) [8–11] has been investigated by several research groups [12]. A reversible capacity (C rev ) of 100–1000 mAh/g has been reported, depending on the sample processing and annealing conditions. The consumers and NASA are in constant demand for micro batteries; thinner, lighter, space-effective and shape, flexible batteries with a larger autonomy. Use of high surface area tubular nano-structures of SWCNTs as Li + insertion anode materials have great potential on the develop- ment of high efficiency electrodes for Li-ion batteries [13–17]. The small size and tubular shape of the SWCNTs electrodes signifi- cantly decrease the effects of concentration polarization at these battery electrodes, resulting in electrodes with high energy density and high power density. Since the anode material of choice for Li-ion batteries is carbon, we are interested in learning if the SWCNTs devices prepared by the self-assembly/condensation reaction method can reversibly intercalate Li + . The self-assembly process allow the sequential construction of reproducible, stable, nanostructural arrays of single wall carbon nanotubes integrated to the modified platinum electrode surface. This new type of highly oriented carbon nanotube device is expected to facilitate intercala- tion reactions due to its host lattice with a central canal. This suggests the possibility of an additional increment of Li ions inter- calation capacity because of the higher surface area-to-unit volume. In this work, self-assembled monolayer (SAM) techniques were used to chemically attach SWCNTs to platinum electrodes through 4-aminothiophenol SAM at Pt electrodes [14,18]. The 1572-6657/$ - see front matter Ó 2013 Published by Elsevier B.V. http://dx.doi.org/10.1016/j.jelechem.2013.06.011 ⇑ Corresponding author. Tel.: +1 787 764 000014807; fax: +1 787 756 8242. E-mail addresses: carlos.cabrera2@upr.edu, ccabrera@uprrp.edu (C.R. Cabrera). Journal of Electroanalytical Chemistry 704 (2013) 242–248 Contents lists available at SciVerse ScienceDirect Journal of Electroanalytical Chemistry journal homepage: www.elsevier.com/locate/jelechem