Carbon armour with embedded carbon dots for building better supercapacitor electrodes

The microstructure design of electrode material is a crucial point to optimize the supercapacitor’s electrochemical properties.In this work,a Bi-based nanocomposite with a three-layer structure(Bi–Bi_(2)O_(3)@carbon armour(CA)/carbon dots(CDs))is synthesized and investigated.This material inherits high capacitance and high activity from bismuth-based materials,the coated CA protects the structure from complete oxidization and improves surface hydrophilicity.Furthermore,CDs in CA can enhance the ion conduction efficiency between the catalyst,carbon membrane,electrolyte.As a consequence,the specific capacitance of the electrode reaches 973 F·g^(−1)under 1 A·g^(−1),the energy density achieves 32.5 Wh·kg^(−1)with a power density of 266.9 W·kg^(−1),with impressive electrochemical stability that Coulomb efficiency of the electrode remains about 100%after 5000 cycles.Furthermore,in-situ Fourier transformation infrared(FT-IR)analyzes the structure evolvement of the material during synthesis and finds that the annealing process of the material removes a great number of oxygen-containing groups of CA and CDs,generating oxygen vacancies,defects,thus active sites,which enhance the capacitance of the material.