Carbon Nanopaper Produced from Carbon Nanotubes/Resorcinol–Formaldehyde Xerogel Nanocomposite for Electrochemical Supercapasitors

Abstract

The nanocomposite of resorcinol–formaldehyde xerogel (RF-xerogel) and carbon nanotubes after carbonization at 800°С was obtained in the form of composite carbon nanopaper (CCNP) with a thickness of 100–300 microns, a density from 0.1 to 0.5 g/cm2 and an electronic conductivity of more than 10 S/cm. According to the low temperature nitrogen adsorption data, the microporous structure of the nanopaper is formed by carbonized RF-xerogel, and the mesoporous structure is formed by the nanotube framework. The specific surface area of the nanopaper calculated by the method of nonlocal density function theory (NLDFT) exceeds 600 m2/g. The main contribution to the specific surface area of CCNP is made by pores with a width of ~0.7 nm, therefore, electrodes for a supercapacitor made of such paper are quite effective only in aqueous solutions of H2SO4 and KOH with small sizes of solvated ions. A technique for nanopaper activation with potassium hydroxide has been developed for the use of CCNP with organic electrolytes. The maximum specific surface area (NLDFT method) of activated CCNP reaches 1182 m2/g with a loss of carbon xerogel mass of ~25%. At the same time, the pore surface area of more than 1 nm width increases from 350 m2/g in CCNP to 685 m2/g in activated CCNP. Nanopaper has mechanical strength, pretty cheap and convenient for use in supercapacitors.