Layer-by-layer assembled free-standing and flexible nanocellulose/porous Co3O4 polyhedron hybrid film as supercapacitor electrodes

Free-standing nanocellulose/ZIF-67 derived porous Co3O4 polyhedron hybrid dual-layer films were layer-by-layer successfully assembled by a water-based paper-making process. Nanocellulose (NFC) not only served as flexible substrate, but also it substituted expensive polymer binders to reduce the cost in the dual-hybrid film electrodes. Besides, the NFC/porous Co3O4 polyhedron composite (NPC) layer replaced the traditional metal current collector to be a free-standing electrode. The flexible NPC-60 film electrode (the ratio of porous Co3O4 polyhedron to NFC component was 60:30) had a higher capacitance (594.8 mF cm(-2) at 5 mV s(-1) in 6 M KOH) than other samples, and a power density of 799.97 W center dot kg(-1) at the energy density of 18.75 Wh center dot kg(-1). With the increase of NFC content, the hybrid film can be bent and rolled demonstrating that the hybrid film has good flexibility and foldability. This work provides an insight perspective for metal organic framework (MOF)-derived metal oxide powders to form flexible and free-standing supercapacitor electrodes.

Automated summary

Dual-layer films of free-standing nanocellulose/ZIF-67 derived porous Co3O4 polyhedrons were successfully assembled using a water-based paper-making process. Nanocellulose served as a flexible substrate and reduced the cost by replacing expensive polymer binders, while the NFC/porous Co3O4 polyhedron composite layer acted as a free-standing electrode with higher capacitance and power density. The hybrid film showed good flexibility and foldability with increasing NFC content, providing insights into flexible and free-standing supercapacitor electrodes derived from MOF-derived metal oxide powders.