Combined effect of carbon nanotubes and polypyrrole on the electrical properties of cellulose-nanopaper

In the present study, 2,2,6,6,-tetramethylpiperidine-1-oxyl (TEMPO)-oxidized cellulose nanofibers (CNF) were combined with multi-walled carbon nanotubes (MWCNTs) and with hybrid MWCNT/polypyrrole to produce a variety of binary and ternary formulations of conductive nanopapers. By following a simple mixing/sonication/filtering process, a homogeneous and well-distributed CNF-MWCNT nanostructure was formed, resulting in a nanopaper of strong mechanical properties (141 MPa tensile strength and 9.41 GPa Young’s modulus) and good electrical conductivity (0.78 S cm−1), for the formulation with 50 wt% of MWCNT. The subsequent in situ polymerization of pyrrole in CNF-MWCNT mixtures produced ternary multiphase CNF-MWCNT-PPy nanopapers with much improved electrical conductivity (2.41 S cm−1) and electrochemical properties (113 F g−1 specific capacitance), even using little amounts of MWCNTs. With these materials, improved hybrid capacitors can be designed. The article presents a trend for the application of cellulose nanofibers in the field of green and flexible electronics.