Single Wall Carbon Nanotubes/Polypyrrole Composite Thin Film Electrodes: Investigation of Interfacial Ion Exchange Behavior

Abstract

Single-wall carbon nanotubes/polypyrrole (SWCNT/PPy) composite thin-film electrodes were prepared by electrodeposition of the pyrrole monomer on a porous network made of SWCNT bundles. Electrode/electrolyte interface, which is intimately related to the pseudocapacitive charge storage behavior, is investigated by using coupled electrogravimetric methods (electrochemical quartz crystal microbalance (EQCM) and its coupling with electrochemical impedance spectroscopy, Ac-electrogravimetry), in a 0.5 M NaCl electrolyte (pH = 7). Our results show that the range of usable potential is greater for composite SWCNT/PPy films than for SWCNT films, which should allow a higher storage capacity to be obtained. This effect is also confirmed by mass variation measurements via EQCM. The mass change (corresponding to the amount of (co)electroadsorbed species) obtained with composite SWCNT/PPy films is four times greater than that observed for pristine SWCNT films if the same potential range is examined. The permselectivity is also greatly improved in the case of composite SWCNT/PPy films compared to SWCNT films; the former shows mainly cation exchange preference. The quantities of anions estimated by Ac-electrogravimetric measurements are much lower in the case of composites. This corroborates the better permselectivity of these composite SWCNT/PPy films even with a moderate amount of PPy.

Carbon-Based Materials for Energy Storage Devices: Types and Characterization Techniques

“…The capacitive behavior in nanocomposite carbon film electrodes was also investigated by Escobar-Teran et al [5]. The EQCM technique was used to investigate the electrochemical behavior of SWCNT/PPy composite electrodes in aqueous electrolyte NaCl 0.5 M (Figure 13).…”

“…In EDLC, the charge is stored by electrostatic interaction between electrolyte ions and the surface of electrodes, typically using carbon materials as electrodes. In pseudocapacitors, the charge is stored by fast and reversible faradaic redox reactions between the electrolyte and electroactive species on the surface of the electrode, generally using conducting polymers (CPs) and transition metal oxide materials as electrodes [5]. Finally, another type of supercapacitor is the so-called hybrid capacitor, where the charging mechanism is due to electrostatic interactions and faradaic reactions [14] (See Figure 2).…”

“…Furthermore, both species (Li + and K + ) are electroadsorbed in their hydrated form but they differ in the degrees of hydration. The capacitive behavior in nanocomposite carbon film electrodes was also inves gated by Escobar-Teran et al [5]. The EQCM technique was used to investigate the ele trochemical behavior of SWCNT/PPy composite electrodes in aqueous electrolyte Na 0.5 M (Figure 13).…”

“…According to the authors, these qualitative observations show that the presence of PPy changes the interfacial ion exchange behavior of SWCNTs. The capacitive behavior in nanocomposite carbon film electrodes was also inves gated by Escobar-Teran et al [5]. The EQCM technique was used to investigate the el trochemical behavior of SWCNT/PPy composite electrodes in aqueous electrolyte Na 0.5 M (Figure 13).…”

“…In contrast, supercapacitors store the charge on reversible electroadsorption of electrolyte ions toward the surface of electrodes [4]. Although featuring lower energy density, supercapacitors can provide a high power delivery in a relatively short time and can operate for a high number of charge/discharge cycles and a longer lifetime than batteries [2,5], as shown in the Ragone Plot (Figure 1). These fast and highly reversible storage mechanisms make supercapacitors promising candidates for energy storage devices, which are presently used in a broad range of applications ranging from small devices (watches, sensors, mobile, headphones, and others) [6] to large-size cells for automotive transportation such as electric car and buses and their charging stations [7].…”