Porous carbon thin films for electrochemical capacitors
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Activation effects on carbon films, derived from commercial aromatic polyimide films (Kapton, DuPont), in CO2 atmosphere at 1203 K on capacitance properties were studied. Two thicknesses of polyimide films were used: 7 and 25 gm. Pore formation during the activation process progresses in two steps due to the existence of a denser surface layer and a more porous core material. In the first step micropores are opening in the dense surface region of the material with average pore diameter smaller than 1 nm. During the second step, mesopores start opening, while micropore volume remains constant with the average micropore diameter of over 1 nm, producing bimodal texture. The first step finishes after 30 min for the thinner samples while for the thicker samples it finishes after 60 mm of activation. As a consequence of such textural changes during activation, the thicker sample has a maximum areal capacitance of 0.35 F/cm(2). The thinner sample activated for 30 min has a maximum volumetric ...capacitance of 220 F/cm(3) and achieves a maximum gravimetric capacitance of 240 F/g when the texture becomes bimodal after 240 min of activation. These results confirm that activation of carbonized Kapton films gives promising electrode materials for supercapacitors. (C) 2013 Elsevier Ltd. All rights reserved.
Source:Carbon, 2013, 64, 456-463
- Physics and Chemistry with Ion Beams (RS-45006)
- Nanostructured Functional and Composite Materials in Catalytic and Sorption Processes (RS-45001)
- Joint Institute for Nuclear Research (JINR), Dubna, Russian Federation, Ministry of Education and of the Republic of Serbia