Construction of hierarchical porous derived from the cellulose nanofiber / graphene / Zn/Co ZIF 3D conductive carbon aerogels for high-performance supercapacitors

Porous carbon aerogels derived from abundant biomass, which possess a unique structure, a high specific surface area and heteroatom doping, are a promising electrodes material for supercapacitors (SCs). In this study, an innovative hierarchical porous material comprising cobalt decorated porous carbons derived from cellulose nanofiber / graphene / Zn/Co ZIF carbon aerogels (CRZCs) has been successfully synthesized by directional freeze drying and carbonization methods. Cellulose nanofibers (CNFs) and graphene (rGO) layers play not only a supporting role, but also an internal storage site for electrolytes, contributing to the diffusion of electrolytes to the surface of active substances, at the same time enhance hydrophilicity of the aerogel and contribute to uniformly disperse Zn/Co ZIF. What's more important is that the carbon aerogels possess hierarchical porous involving micropores, mesopores and macropores, which further aid electrolyte penetration and ion storage. Furthermore, benefiting from the synergetic effect of hierarchical porous, high surface area, high conductivity, the prepared CRZC electrode obtains a high specific capacitance (364.6 F g⁻¹ at 1 A g⁻¹), an extraordinary capacitance retention rate (83.4 % at 10 A g⁻¹). Simultaneously, the assembled supercapacitor by CRZC 900 exhibits a high specific capacitance (121.4 F g⁻¹ at 0.5 A g⁻¹), good charging/discharging rates, and remarkable cycling stability (78.9 % capacitance retention over 10000 cycles). The energy density up to 18.9 Wh kg⁻¹ is achieved at power density of 288.4 W kg⁻¹, indicating its comprehensive applicability in energy storage. Finally, our results provide a general approach to construct hierarchical porous carbon aerogels for high-performance supercapacitors.