Dual-Active-Site NiCo2S4@CoP/Ni2P Ternary Heterojunction for High-Performance Hybrid Supercapacitors

Abstract

The rational design of electrode materials that integrate high capacity, excellent rate capability, and long cycle life is crucial for advancing supercapacitor development. In this study, we successfully constructed a NiCo₂S₄@CoP/Ni₂P (NCNP) ternary heterojunction composite with a hollow structure via a templating synthesis strategy for use as a supercapacitor electrode. This material intimately combines highly conductive and high-capacity NiCo₂S₄ with bimetallic phosphides, viz., CoP/Ni₂P, known for their excellent rate performance at the nanoscale, forming a triphase heterostructure rich in interfaces and sulfur vacancies. Physicochemical characterization revealed that the ternary heterointerfaces in the NCNP heterojunction composite induce significant lattice distortion and electronic structure reconstruction, producing a strong built-in electric field that substantially enhances electron/ion transport kinetics. Simultaneously, the synergistic effect of the dual active sites from CoP and Ni₂P boosts the redox reaction activity of the system. Electrochemical tests revealed that the NCNP electrode exhibits a high specific capacitance of 1061 F g⁻¹ at 1 A g⁻¹, retains 93% of its capacity at 10 A g⁻¹, and possesses outstanding cycling stability (86% capacity retention after 10,000 cycles). First-principles calculations further indicated that the ternary interface possesses the smallest bandgap (0.0005 eV) and optimal charge distribution, significantly enhancing the electrical conductivity and intermediate adsorption capability of the material. The assembled NCNP//AC (active carbon) hybrid supercapacitor achieves an energy density of 83 Wh kg⁻¹, demonstrating promising application prospects.