Defect-rich hierarchical porous carbon prepared by homogeneous activation for high performance capacitive deionization

Defect engineering has emerged as an effective approach for modulating the electronic structure and physicochemical properties of carbon materials. Porous carbon materials with abundant defects are regarded as prospective electrode materials for capacitive deionization. Nevertheless, constructing defect-rich carbon materials and revealing the relationship between desalination capacity and intrinsic defects remains a daunting challenge. Herein, the defect-rich interconnected hierarchical porous carbon (IHPC) was fabricated via sol-gel method to form a supramolecular hydrogel containing highly dispersed K+ using coal, polyvinylpyrrolidone, and KOH as raw materials, followed by homogeneous activation. The spectroscopic studies coupled with density functional theory calculations demonstrate that the introduction of intrinsic defects can optimize the distribution of electron density to promote charge transfer, thereby enhancing saline ions adsorption. The plentiful adsorption sites, robust charge transfer kinetics and rapid ion diffusion derived from the multiple advantageous characteristics of IHPC facilitate a high desalination capacity of 31.25 mg g−1 in 800 mg L−1 NaCl solution. Meanwhile, it also presented excellent desalination performances in KCl (31.42 mg g−1), CaCl2 (29.55 mg g−1), and MgCl2 (26.65 mg g−1) solutions. The higher desalination capacity, rapid salt adsorption rate as well as outstanding cycling stability rank the IHPC as a potential candidate for capacitive deionization applications.