Polypyrrole‐decorated, milled carbon fibers‐inserted chitin nanofibers/multiwalled carbon nanotubes flexible free‐standing film for supercapacitors

Abstract A flexible free‐standing film was fabricated using interconnected chitin nanofibers (ChNFs) and multiwalled carbon nanotubes (MWCNTs) as a conductive substrate, by inserting in milled carbon fibers (MCFs) to increase the number of holes and decorating it with polypyrrole (PPy) to improve the capacitance. The synthesis process for the ChNFs/MWCNTs/MCFs/PPy (CMMP) film was simple and effective, for which the 3D structure of ChNFs/MWCNTs/MCFs (CMM) film was first fabricated through vacuum‐filtration followed by adding PPy on the surface of CMM film via in situ polymerization. Field emission scanning electron microscopy showed that the CMMP film had a porous structure similar to aerogel, which was caused by the great size difference between ChNFs/MWCNTs and MCFs. Furthermore, the CMMP film had a high specific capacitance of 362 F g⁻¹ at a scan rate of 5 mV s⁻¹ in 1 mol L⁻¹ sulfuric acid, excellent cycling stability with a retention of 86.6% after 5000 cycles at 2 A g⁻¹, and good thermal stability with a 77% mass residue at 600^°C at the mass ratio of 1:1:0.5:13.38 (Py: 5 mmol). In general, this environmentally‐friendly, simple‐synthesis, high‐performance CMMP film could be widely used in the flexible all‐solid‐state supercapacitor field.