Defect-Induced Atomic Arrangement in CoFe Bimetallic Heterostructures with Boosted Oxygen Evolution Activity

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Developing efficient electrocatalysts for water oxidation is crucial for sustainable energy technologies.
• Bimetallic oxides offer tunable properties but often require optimization for enhanced activity.
• Defect engineering presents a promising strategy to improve catalyst performance.

Purpose of the Study:

• To synthesize novel cobalt-iron bimetallic oxides (CoFeOₓ) with controlled defect structures.
• To investigate the impact of different synthesis atmospheres on the material's composition and morphology.
• To evaluate the electrocatalytic activity of the synthesized materials for water oxidation.

Main Methods:

• Thermally treating metal-organic framework (MOF) precursors under various atmospheres (air, N₂, NaBH₄/N₂).
• Characterization using X-ray absorption spectroscopy and ex situ techniques.
• Electrochemical testing including overpotential, Tafel slope, and turnover frequency measurements.
• Theoretical calculations to understand electronic structure and intermediate binding energies.

Main Results:

• CoFeOₓ-H, synthesized under NaBH₄/N₂, formed a defective CoO/CoFe₂O₄ heterostructure with abundant oxygen vacancies.
• CoFeOₓ-H exhibited superior electrocatalytic activity for water oxidation, with a lower overpotential (192 mV at 10 mA cm⁻²) compared to CoFeOₓ-A.
• The material demonstrated fast reaction kinetics, evidenced by a low Tafel slope (42.53 mV dec⁻¹) and high turnover frequency (785.5 h⁻¹).
• Defect engineering tuned the electronic configuration, reducing oxo intermediate binding energy and promoting efficient electron transfer via the hetero-interface.

Conclusions:

• The defective CoO/CoFe₂O₄ heterostructure in CoFeOₓ-H significantly enhances water oxidation electrocatalysis.
• Defect engineering is an effective strategy to modulate electronic configurations and improve catalyst performance.
• The hetero-interface in CoFeOₓ-H provides abundant active sites and promotes efficient charge transfer, leading to high catalytic activity.