Highly dispersed ultrasmall BiOCl nanoclusters on graphene sheets as high-performance anion-capture electrode for hybrid capacitive deionization

BiOCl nanomaterials, because of their unique layered structure and fascinating physicochemical properties, have attracted enormous attention as anode material for capacitive deionization (CDI) towards the relief of global freshwater scarcity. However, the synthesis of ultrasmall BiOCl nanoclusters remains a considerable challenge, while the effect of crystalline surfaces on the Cl− ion intercalation/deintercalation has not yet been explored so far. In this work, highly dispersed BiOCl nanoclusters with the predominant exposure of (110) and (101) planes on graphene sheets (BiOCl@G) are fabricated by nanoconfinement and air-plasma strategy. On one hand, the ultrasmall BiOCl nanoclusters with size of ∼3 nm significantly increased their atomic utilization and electrochemical active sites, whereas the preferred crystalline planes of (110) and (101) favored the Cl− intercalation/deintercalation process within BiOCl. On the other hand, the dominant mesopores, along with a large interlayer distance (∼0.4 nm) between exfoliated graphene sheets, ensured the fast ion transport-adsorption at BiOCl/solution interface. With these novel structural features, the BiOCl@G possesses excellent figure-of-merits in terms of the Cl−-adsorption capacity (109.8 mg g−1), adsorption rate (0.110 mg g−1 s−1), energy consumption, and CDI cycling stability. These results provide new fundamental insights for developing high performance BiOCl-graphene nanocomposites used in CDI desalination and beyond.