Nanostructuring Nickel–Zinc–Boron/Graphitic Carbon Nitride as the Positive Electrode and BiVO₄-Immobilized Nitrogen-Doped Defective Carbon as the Negative Electrode for Asymmetric Capacitors

Rationally designed compounds with exceptional surface functionalities are greatly necessary for efficient energy-storage technologies. Herein an aqueous battery-type hybrid supercapacitor device is fabricated based on amorphous nickel–zinc–boron/graphitic carbon nitride (Ni–Zn–B/g-C3N4) nanosheet network structures as the cathode and a bismuth vanadate-anchored carbon nanotube matrix with nitrogen dopants and defect sites (BiVO4/NC) as the anode. Interconnected nanosheet-assembled Ni–Zn–B/g-C3N4 porous networks are developed via a scalable liquid-phase reduction method, while the BiVO4/NC nanocomposite frameworks are prepared by a simple chemical precipitation route and annealing treatment. Because of the unique compositional and structural features as well as enhanced electrochemical properties, the as-assembled Ni–Zn–B/g-C3N4//BiVO4/NC aqueous alkaline device with a large working potential of 1.6 V exhibits a remarkable energy-storage capability with a high energy density of 78.4 Wh kg–1 and a power density of 907.7 W kg–1 together with a good cyclic performance (85.3% retention after 8000 cycles). Considering the intriguing results and reasonable design of the cathode and anode materials, this work provides a significant prospect for designing a high-performance energy-storage system. The intrinsically enhanced electrochemical performances of heterostructured Ni–Zn–B/g-C3N4 and BiVO4/NC demonstrate their potential utilization in energy-storage systems.