Influence of the PAni morphology deposited on the carbon fiber: An analysis of the capacitive behavior of this hybrid composite

Abstract

a b s t r a c t CF/PAni composites were synthesized using the polymerization chemistry. Three different deposition times were used in the synthesis, such as: 30, 60 and 90 min. The morphology and the structure of composites were analyzed by SEM and Raman spectroscopy, respectively. The influence of the mass of polymer deposited on the carbon fiber, with respect to the values of specific capacitance (C sp ) was analyzed by electrochemical experiments. The optimum value of the C sp was obtained for CF/PAni-30 min (C sp = 188 Fg À1 ). This fact is related to the lower charge transfer resistance, due to its more homogeneous morphology and thin layer polyaniline.

Enhanced Adsorptive Properties and Pseudocapacitance of Flexible Polyaniline-Activated Carbon Cloth Composites Synthesized Electrochemically in a Filter-Press Cell

“…The evolution of the specific capacitance observed in this work is in agreement with the results reported earlier by other researchers [12,16,21,23,62]. It has been generally shown that the capacitance is enhanced by either smooth homogeneous PAni coatings of small thickness [12] or nanofiber-shaped assemblies with a certain degree of 3D order and small diameter [22,23] obtained at low PAni loading densities. Such thin nanostructures are believed to provide fast access of electrolyte and shortened path lengths for ion and electron transport.…”

“…Three-dimensional networks of nanofibrilar or nanowire structures seem the most frequently encountered morphology for PAni deposited on high surface area carbon substrates (e.g., carbon fibers or cloths), either by electrochemical [20,21,62,63] or conventional in-situ chemical polymerization [22,23,24]. However, in agreement with our results, some authors have obtained smooth dense layers [8,63] or a transition from this morphology to irregular or randomly connected nanofibrilar aggregates upon extending the polymerization time [12,62]. It has also been reported that long reaction time [23] or prolonged galvanostatic oxidation [20] lead to incontrollable growth among carbon fibers and result in a detrimental effect via peeling-off from the carbon surface.…”

“…A simple control of the PAni loading could be achieved by passing different amounts of charge, i.e., by adjusting the elapsed electropolymerization time. The highly porous carbon fabric provides the hybrid composite material with high specific surface area, flexibility and mechanical strength to mitigate the stress associated with polymer volume changes accompanying doping/dedoping [11,12,22], while PAni adds some new enhanced characteristics related to its reversible redox properties and electron conductivity [2,12,62].…”

“…However, PAni has the main shortcomings of a relatively low porosity, specific surface area, slow degradation, and poor mechanical stability because of volume changes produced upon repeated charge/discharge process [2,4,11,12]. Composites of PAni with carbon materials, metal oxides, natural and modified clay minerals, zeolites or mesoporous silica [2,4,9,10], have been extensively investigated with the goal of overcoming these disadvantages and further improving existing properties via synergistic effects.…”

“…Carbons are outstanding versatile materials with regards to their use as composite supports because of the wide availability of allotropes, microtextures, 0 to 3D dimensionality, and macroscopic forms. In addition, their excellent chemical and thermal stability, good electrical conductivity, large specific surface area, wide range of pore structures, and mechanical strength [11,12] make them particularly suitable as composite constituents for electrochemical applications or environmental adsorbents. To date, much work has been undertaken on PAni composites with carbon nanotubes [13,14], graphene/reduced graphene oxide nanosheets [4,13], porous carbon foams or rods [15,16] and activated carbon fibers [11,17] or powders [18,19].…”