Hierarchical heterostructure engineering of amorphous nickel boride nanoparticles decorated N-doped NiMoO hollow nanostructures with enhanced interfacial conductivity for high-performance hybrid supercapacitors.

Constructing heterostructured electrode materials with unique nanoarchitectures and tailored electronic properties is regarded as a practicable approach to boost the energy density of hybrid supercapacitors (HSCs). Herein, a novel heterostructure comprising semiconductive nitrogen-doped nickel molybdate (N-NiMoO) hollow nanostructures and metalloid nickel boride (NiB) nanoparticles is designed and synthesized. Theoretical simulations and experimental analyses reveal that the nitrogen doping enhances the electrical conductivity of N-NiMoO. In particular, the formation of an ohmic contact interface between N-NiMoO and NiB reduces the barrier to electron/ion transport across the interface, thereby considerably improving the electrochemical reaction kinetics. Furthermore, the surface decoration of the N-NiMoO hollow nanostructures with the NiB nanoparticles provides additional electroactive sites and enhances the overall electrochemical performance of the N-NiMoO@NiB heterostructures. Consequently, the constructed N-NiMoO@NiB heterostructures exhibit enhanced specific capacities (932 C g at 1 A g and 709 C g at 10 A g, respectively) and cyclic stability (93.6 % capacity retention after 5000 cycles). Moreover, the assembled HSC device using N-NiMoO@NiB as the positive electrode can deliver an energy density of up to 53.1 Wh kg at 802 W kg and maintain 95.0 % capacity after 5000 cycles. These findings provide valuable insights for optimizing interface design and heterojunction engineering in metal-boride/molybdate-based composite electrodes for advanced HSCs.