Metal-organic framework (MOF)-derived nanoporous carbons (NPCs) and porous metal oxide nanostructures or nanocomposites have gathered considerable interest due to their potential use in supercapacitor (SCs) applications, owing to their precise control over porous architectures, pore volumes, and surface area. Bimetallic MOFs could provide rich redox reactions deriving from improved charge transfer between different metal ions, so their supercapacitor performance could be further greatly enhanced. In this study, “One-for-All” strategy is adopted to synthesize both positive and negative electrodes for hybrid asymmetric SCs (ASCs) from a single bimetallic MOF. The bimetallic Zn/Co-MOF with cuboid-like structures were synthesized by a simple method. The MOF-derived nanoporous carbons (NPC) were then obtained by post-heat treatment of the as-synthesized Zn/Co-MOF and rinsing with HCl, and bimetallic oxides (ZnCo₂O₄) were achieved by sintering the Zn/Co-MOF in air. The as-prepared MOF-derived NPC and bimetallic oxides were utilized as negative and positive materials to assemble hybrid ASCs with 6 M KOH as an electrolyte. Owing to the matchable voltage window and specific capacitance between the negative (NPC) and positive (ZnCo₂O₄), the as-assembled ASCs delivered high specific capacitance of 94.4 F/g (cell), excellent energy density of 28.6 Wh/kg at a power density of 100 W/kg, and high cycling stability of 87.2% after 5,000 charge-discharge cycles. This strategy is promising in producing high-energy-density electrode materials in supercapacitors.

The exploration of highly abundant and available biomass wastes as sustainable precursors through a scalable and cost-effective synthesis strategy is extremely important for novel materials development in energy storage and conversion technologies. Herein, we have successfully fabricated hierarchical micro-/mesoporous carbons (HMMC) from low-cost and eco-friendly agricultural residues via an easy method. The highly hierarchical porous carbons were obtained from rice husk via NaOH-assisted hydrothermal pre-treatment followed by carbonization/activation process. The NaOH-assisted hydrothermal treatment removed ash content and facilitated the development of pores, especially the mesopores, resulting in hierarchical porous carbons with high specific surface area, large pore volume and high ratio (49.3%) of mesopores. These hierarchically structural advantages guarantee the excellent performances of the resultant porous carbons as electrodes for supercapacitors. The rice husk-derived HMMC electrode exhibit a maximum capacitance of 302.2 F g⁻¹ at a current density of 1 A g⁻¹ in a three-electrode system with 6 M KOH as electrolyte, which is significantly better than 193.7 F g⁻¹ at 1 A g⁻¹ obtained on rice husk-derived microporous carbons via direct carbonization and activation. Moreover, the NaOH-assisted HMMC electrodes also show good cycle stability. These results demonstrated that NaOH-assisted hydrothermal pre-treatment is a facile and effective way to produce hierarchical porous carbons from natural biomass wastes with improved electrochemical performances for supercapacitors.