Vertically Aligned\nBismuthene Nanosheets on MXene\nfor High-Performance Capacitive Deionization

Abstract

Capacitive\ndeionization has been considered as a promising\nsolution\nto the challenge of freshwater shortage due to its high efficiency,\nlow environmental footprint, and low energy consumption. However,\ndeveloping advanced electrode materials to improve capacitive deionization\nperformance remains a challenge. Herein, the hierarchical bismuthene\nnanosheets (Bi-ene NSs)@MXene heterostructure was successfully prepared\nby combining the Lewis acidic molten salt etching and the galvanic\nreplacement reaction, which achieves the effective utilization of\nthe molten salt etching byproducts (residual copper). The vertically\naligned bismuthene nanosheets array evenly in situ grown on the surface\nof MXene, which not only facilitate ion and electron transport as\nwell as offer abundant active sites but also provide strong interfacial\ninteraction between bismuthene and MXene. Benefiting from the above\nadvantages, the Bi-ene NSs@MXene heterostructure as a promising capacitive\ndeionization electrode material exhibits high desalination capacity\n(88.2 mg/g at 1.2 V), fast desalination rate, and good long-term cycling\nperformance. Moreover, the mechanisms involved were elaborated by\nsystematical characterizations and density functional theory calculations.\nThis work provides inspirations for the preparation of MXene-based\nheterostructures and their application for capacitive deionization.