Defect-Engineered NiCo-S Composite as a Bifunctional Electrode for High-Performance Supercapacitor and...

Area of Science:

• Materials Science
• Electrochemistry
• Nanotechnology

Background:

• Defect engineering is crucial for enhancing nanomaterial properties.
• Introducing dual defects efficiently remains a challenge.
• Metal sulfides are promising for energy applications.

Purpose of the Study:

• To develop a facile method for introducing dual defects (Fe doping and S vacancies) into bimetallic nickel cobalt sulfide (NiCo-S) composites.
• To investigate the electrochemical performance of the engineered Fe-NiCo-S as electrode material for supercapacitors and the oxygen evolution reaction (OER).

Main Methods:

• A two-step solvothermal method was employed to synthesize Fe-doped NiCo-S with sulfur vacancies.
• Electrochemical performance was evaluated using cyclic voltammetry, galvanostatic charge-discharge, and electrochemical impedance spectroscopy.
• Density functional theory (DFT) calculations were used to understand the electronic structure modifications.

Main Results:

• The Fe-NiCo-S nanosheets exhibited a high specific capacitance of 2779.6 F g⁻¹ at 1 A g⁻¹ and excellent rate capability (1627.2 F g⁻¹ at 10 A g⁻¹).
• A hybrid supercapacitor device demonstrated a high energy density of 56.0 Wh kg⁻¹ and retained 96.5% capacity after 10,000 cycles.
• The Fe-NiCo-S composite showed an ultralow OER overpotential of 247 mV at 10 mA cm⁻².
• DFT calculations confirmed that defects enhance electron transfer near the Fermi level.

Conclusions:

• The facile two-step solvothermal method effectively introduces dual defects into NiCo-S composites.
• Fe-NiCo-S exhibits superior electrochemical performance for supercapacitors and OER applications.
• This work provides a viable strategy for designing advanced electrode materials for energy storage and conversion.