Carbothermal Diffusion Reaction Synthesis of CrN/carbon Nanofiber for Efficient Electrosorption of Fluoride Ions from Water

Development of novel electrode materials with the integration of structural and compositional merits can essentially improve the electrosorption performance. Herein, we demonstrate a new strategy, named as carbothermal diffusion reaction synthesis (CDRS), to fabricate binder-free CrN/carbon nanofiber electrodes for efficient electrosorption of fluoride ions from water. The CDRS strategy involves electrospinning MIL-101(Cr) particles with polyacrylonitrile (PAN) to form one-dimensional nanofiber, followed by spatial-confined pyrolysis process in which the nitridation reaction occurred between nitrogen element from PAN and chromium element from MIL-101(Cr), resulting macroscopic, free-standing electrodes with well dispersed ultrafine CrN nanoparticles on porous nitrogen enriched carbon matrix. As expected, the F⁻ adsorption capacity reached 47.67 mg g⁻¹ and there was no decrease in F⁻ removal after 70 adsorption regenerations in 50 mg L⁻¹ F⁻ solution at 1.2 V. The adsorption mechanism of F⁻ was explored by X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT). The enhanced F⁻ adsorption capacity was achieved by the reversible Cr⁴⁺/Cr³⁺ redox pair provided by CrN and the electrical double layer capacitance produced by carbon skeleton. This study provides guidance on synergistic modulation of shaping and composition optimization of novel functional materials for electrosorption, catalysis, and supercapacitor applications.

Graphical abstract