One-pot synthesis of Bi/BiVO₄ yolk-shell and hollow nanospheres as novel negative electrode material for supercapacitor

Currently, the lack of negative electrodes with high specific capacity has hindered the further improvement of supercapacitors in the aspect of energy density. Herein, for the first time, Bi/BiVO₄ yolk-shell and hollow nanospheres (Bi/BiVO₄ YSHNs) were fabricated by a one-pot hydrothermal route. When this novel heterostructure material was employed as negative electrode for supercapacitor, high specific capacity of 1465 C g⁻¹ at 1 A g⁻¹ was obtained. Furthermore, excellent rate capability (728 C g⁻¹ at 26 A g⁻¹) and better cycling stability (90% retention after 2000 cycles) were also achieved. The outstanding electrochemical performance of the Bi/BiVO₄ electrode should be resulted from the distinctive configuration and synergistic effect of all the composite components. Density functional theory (DFT) calculation revealed charge redistribution as well as stronger electron accumulation between Bi and BiVO₄, which enhanced the electrical conductivity of the electrode, so its electrochemical performance was boosted. More significantly, by using Mn − Ni − S/rGO/NF nanocomposite as positive electrode and Bi/BiVO₄ YSHN as negative electrode, the as-assembled asymmetric capacitor (ASC) delivered admirable energy density of 86.2 Wh kg⁻¹ at a power density of 751.4 W kg⁻¹. Therefore, besides a new negative electrode material with heterostructure for supercapacitor, this work also provides a novel approach to fabricate yolk-shell and hollow nanospheres.