Wrinkled hierarchical porous carbon spheres with interconnected multi-cavity for ultrahigh capacitive deionization

As one of the most promising electrode materials for capacitive deionization (CDI), the development of carbon materials with controllable pore structure and continuous mass production is essential for their practical application. Herein, a facile ultrasonic spray pyrolysis method was developed to synthesize surface-functionalized wrinkled hierarchical porous carbon spheres (HCS) with unique interconnected multi-cavity structures. The wrinkled and interconnected multi-cavity hierarchical pores of the HCS play a crucial role in providing accessible ion adsorption sites and promoting ion diffusion and storage in the "multi-cavity warehouse". The carboxyl groups on the surface of HCS generate a negative charge that promotes the adsorption of cations. The optimized HCS possesses outstanding desalination capacity (114.25 mg g-1), fast adsorption rate (6.57 mg g-1 min-1), and superior cycling stability (95%). Meanwhile, the HCS exhibited impressive desalination capacities in brackish water. Furthermore, the density functional theory calculation results confirmed that the synergistic effect of carboxyl groups and defects significantly enhanced the Na+ adsorption capacity and facilitated ion diffusion. This study extends the synthesis method of surface-functionalized hierarchical porous carbon, which is expected to facilitate the development of CDI electrode materials.