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.
Highlights
Polymers and polymeric composites are a unique class of materials, extensively used in numerous fields of applications such as electrochemical energy storage and conversion [1].Due to their peculiar physicochemical and mechanical properties, these materials have been stimulating new research that aims at refining their structural, morphological and compositional characteristics to achieve the desired properties required for electrode or electrolyte materials used in energy devices [2,3].Among them, supercapacitors (SCs) can provide a large amount of power in a relatively short time and can operate for a very high number of charge/discharge cycles and a longer lifetime than batteries [4,5]
The SWCNT/PPy composite electrodes are prepared in a two-step process
Evaluating the electrochemical signatures of the pristine SWCNT and SWCNT/PPy composites does not allow us to distinguish the improvements in terms of interfacial species transfer behavior
Summary
Polymers and polymeric composites are a unique class of materials, extensively used in numerous fields of applications such as electrochemical energy storage and conversion [1] Due to their peculiar physicochemical and mechanical properties, these materials have been stimulating new research that aims at refining their structural, morphological and compositional characteristics to achieve the desired properties required for electrode or electrolyte materials used in energy devices [2,3]. Supercapacitors (SCs) can provide a large amount of power in a relatively short time and can operate for a very high number of charge/discharge cycles and a longer lifetime than batteries [4,5] These versatile attributes have led to their incorporation in a wide range of applications (such as city transit buses with stop-and-go driving, cranes and forklifts [6]). As for the pseudocapacitors, energy is stored by fast and reversible redox reactions between the electrolyte and electroactive species on the electrode surface at characteristic potentials, commonly employing transition metal oxides and conducting polymers (CPs) as electrode materials [10,11]
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