Hierarchical Porous Carbons Derived from Porous Biomass for High-Performance Capacitive Deionization

Capacitive deionization (CDI) technology is a promising desalination technology with the advantages of low energy consumption, high water recovery, and environmental friendliness. Hierarchical porous carbons (HPCs) have attracted intense interest due to their excellent physicochemical and electrochemical properties. In this work, hierarchical porous biochar materials were prepared through a direct carbonization method using natural porous biomass including lotus petiole (LP), sunflower plate (SP), and lotus seedpod (LS). The effects of pore structures, surface properties, and electrochemical properties of these biochars on the desalination performance were investigated. The results showed that the biochar prepared from SP (SPC) had a more suitable aperture structure, better surface wettability, higher surface charge, and larger specific capacitance than those of other biochars prepared from LP and LS (LPC and LSC), which resulted in better desalination performance (9.24 mg·g –1 ) and charge efficiency (77%) of SPC. The desalination processes of the three biochars all conformed to pseudo-first-order kinetics, indicating that the CDI process was mainly an electrostatic mechanism. This work shows that biochars could be engineered and explored broadly as low-cost and environmentally friendly HPC electrode materials for high-performance CDI.