Pore engineering: Structure-capacitance correlations for biomass-derived porous carbon materials

As the world’s demand for green energy storage systems continues to increase, electrochemical double-layer supercapacitors based on porous carbon electrodes are receiving more attention than ever. Porous carbon materials can be designed and synthesized from biomass residues/extracts through various technologies, which realizes the value-added utilization of biomass and meets the targets of circular economy. Pore characteristics are particularly important for the capacitive performance of carbon-based electrodes. This review outlines the biomass-derived porous carbon materials and their corresponding capacitive properties, which are divided into biomass-derived ultra/super-microporous carbon, mesoporous carbon, macroporous carbon and hierarchical porous carbon according to the category of pore size. The synthesis methods, pore characteristic testing probes/calculation models and capacitance performance are discussed in detail, and the corresponding advantages and bottlenecks are pointed out critically. Emphasis is laid on the research status and development trend of biomass-derived hierarchical porous carbon materials, including the effects of the structure and composition of biomass precursors, advanced nanotechnologies and the proportion of various pores in carbonaceous products on the capacitance performance. Finally, the coping strategies are proposed for the further development of high capacitance biomass-derived porous carbon materials.