Porous CuS@CuSe heterostructure cathode in capacitive deionization for exceptional copper ion electrosorption from wastewater

Water pollution is a pressing environmental concern in today's world. Among the various pollutants found in aquatic environments, heavy metals, due to their high activity and wide range, are of particular concern. In the field of aqueous copper ion batteries, CuSe and CuS have been recognized as excellent copper storage materials. Selenium (Se) exhibits remarkable cyclic stability but limited reversible capacity, whereas sulfur (S) shows superior reversible capacity but inadequate cyclic stability. In this study, we synthesized a heterogeneous hollow core–shell structure known as CuS@CuSe. This structure was achieved by utilizing Cu2O as a template for layer-by-layer sulfuration and selenisation processes. The CuS@CuSe structure provides more electrically active sites and lowers the energy barrier for reactions. As a result, when used as cathode materials in capacitive deionization (CDI), CuS@CuSe demonstrates exceptional electroadsorption capacity (647.0 mg g−1), a high ion transport rate of 17.1 mg g−1 min−1, and superior cycling properties. The adsorption mechanism of CuS@CuSe was investigated through characterization techniques and density functional theory (DFT) calculations. These findings not only contribute to the understanding of the adsorption process but also provide valuable insights for the design and development of effective electrode materials capable of selectively capturing copper ions from wastewater.