Production of Vermiculite Nanosheets by Liquid Exfoliation for Efficient Capacitive Deionization

Capacitive deionization (CDI) is an enormous potential versatile platform for energy-efficient seawater electro-desalination technology. However, traditional carbon materials and charge transfer materials have problems such as low capacity, serious co-ionic effect, ion leakage of transition metal, and rigorous preparation conditions. Vermiculite, a natural clay with a two-dimensional layered structure, offers advantages such as cation exchange capacity, wide availability, environmental friendliness, nontoxicity, and a negatively charged surface. Here, 2D vermiculite nanosheets (VMs) are exfoliated from bulk vermiculite via a sustainable ion exchange process that is low cost, green, and nontoxic. Compared with bulk vermiculite, the VMs possess an abundance of internal negative surface charge, which is beneficial for charge transfer, local conductivity, and more available active sites for Na⁺ adsorption/desorption in reversible electrochemical processes. Due to the high-density of exposed adsorption sites and rapid Na⁺ transport pathways, the obtained 2D VMs electrode enables a high sodium ion adsorption capacity of 26.56 mg g^-1 at 1.2 V voltage in 500 mg L^-1 salt solution and no secondary pollution of water bodies, which holds significant potential for widespread application in brackish water desalination.