Construction of Ni₃V₂O₈ /CoMoO₄ Core-shell Heterostructures with Urea as Additive and Their Capacitive Properties in Highperformance Asymmetric Supercapacitors

Abstract

In this work, a core–shell heterostructure cathode (Ni₃V₂O₈@CoMoO₄‑A) with a Ni₃V₂O₈ nanowire core and a vertically coated CoMoO₄ nanosheet shell was controllably synthesized by a two‑step hydrothermal method using urea as a morphology regulator. Urea slowly releases OH⁻ ions via a homogeneous precipitation mechanism, which effectively promotes the heterogeneous nucleation and dense growth of CoMoO₄ on the Ni₃V₂O₈ surface. The material presents a well‑developed porous structure and abundant redox sites. Three‑electrode tests show that the electrode exhibits a specific capacitance of 952.1 F·g⁻¹ at 1 A·g⁻¹ with a retention of 94% after 10000 cycles. A CNT/Fe₂O₃ composite anode was prepared by loading α‑Fe₂O₃ nanoparticles onto acidified carbon nanotubes, integrating high conductivity and high pseudocapacitive activity. An asymmetric supercapacitor was assembled with Ni₃V₂O₈@CoMoO₄‑A as cathode and CNT/Fe₂O₃ as anode, which operates stably at a voltage window of 1.4 V. Calculated based on the total active mass of both electrodes, the device delivers an energy density of 80.9 Wh·kg⁻¹ at 750 W·kg⁻¹ and remains 46.2 Wh·kg⁻¹ at 7500 W·kg⁻¹. The capacitance retention reaches 95.9% after 10000 cycles. This work demonstrates that interface engineering and structural regulation can significantly improve the performance of supercapacitors, providing a feasible strategy for high‑performance aqueous energy‑storage devices.