3D grape string-like heterostructures enable high-efficiency sodium ion capture in Ti 3 C 2 T x MXene/fungi-derived carbon nanoribbon hybrids.

2D transition metal carbides and carbonitrides (MXenes) have emerged as promising electrode materials for electrochemistry ion capture but always suffer from severe layer-restacking and irreversible oxidation that restrains their electrochemical performance. Here we design a dual strategy of microstructure tailoring and heterostructure construction to synthesize a unique 3D grape string-like heterostructure consisting of Ti 3 C 2 T x MXene hollow microspheres wrapped by fungi-derived N-doping carbon nanoribbons (denoted as GMNC). The 3D grape string-like heterostructure effectively avoids the aggregation of Ti 3 C 2 T x MXene sheets and enhances the stability of MXenes, providing abundant active sites for ion capture, and an interconnected conductive bionic nanofiber network for high-rate electron transport. In consequence, GMNC achieves a superior adsorption capacity for sodium ions (Na + ) in capacitive deionization (CDI) (162.37 mg g NaCl -1 ) with an ultra-high instantaneous adsorption rate (30.52 mg g -1 min -1 ) at an applied voltage of 1.6 V and satisfactory cycle stability over 100 cycles, which is a strong performer among the state-of-the-art values for MXene-based CDI electrodes. In addition, in situ electrochemical quartz crystal microbalance with dissipation monitoring (EQCM-D) measurement combined with density functional theory (DFT) reveals the mechanisms of the Na + capture process in the GMNC heterostructure. This work opens a new avenue for designing high-performance MXenes with a 3D hierarchical heterostructure for advanced electrochemical applications.