Heterojunction-Induced Facet Reorientation: Decoupling Thermodynamics and Kinetics for Ultrastable Ni₂P-Based...

Area of Science:

• Materials Science
• Electrochemistry
• Nanotechnology

Background:

• Nickel-based phosphides are promising for energy storage but suffer from oxidation and parasitic oxygen evolution reactions (OER) at high voltages.
• These degradation pathways limit the practical application and operational stability of nickel phosphide electrodes in devices like supercapacitors.

Purpose of the Study:

• To develop a novel Ni₂P@Ni-Co PBA heterojunction to suppress material oxidation and OER.
• To enhance the stability and electrochemical performance of nickel phosphide-based electrodes for energy storage applications.

Main Methods:

• Electrostatic self-assembly to induce crystal facet reorientation of Ni₂P nanosheets.
• Density Functional Theory (DFT) calculations to analyze interfacial electronic structure modulation.
• High-Resolution Transmission Electron Microscopy (HRTEM) to characterize passivation layer formation.

Main Results:

• The Ni₂P@Ni-Co PBA heterojunction exhibits enhanced exposure of the active (400) facet, leading to downshifted d-band center and surged density of states at the Fermi level.
• A self-limiting passivation layer forms, thinner at the heterointerface, which inhibits degradation.
• The heterojunction electrode shows a wide voltage window, high specific capacitance (1674.91 F g⁻¹), and enables asymmetric supercapacitors (ASCs) with excellent cycling stability (97.14% after 10,000 cycles).

Conclusions:

• The interfacial reconstruction strategy effectively suppresses oxidation and OER, enhancing electrode stability.
• The developed heterojunction material offers a new paradigm for designing high-performance and durable electrode materials for supercapacitors.
• Flexible solid-state ASCs achieved a wide 1.8 V window and 53.44 Wh kg⁻¹ energy density, demonstrating practical potential.