High-Density Atomic Level Defect Engineering of 2D Fe-Based Metal-Organic Frameworks Boosts Oxygen and Hydrogen...

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Metal-organic frameworks (MOFs) are promising electrocatalysts for water splitting.
• The transition of MOFs to metal oxyhydroxides during catalysis complicates the identification of active sites and affects stability.

Purpose of the Study:

• To engineer defects in two-dimensional Fe-MOFs to create high-density atomic level defects.
• To understand the role of these defects and the subsequent phase transformation in electrocatalytic water splitting.

Main Methods:

• On-purpose defect engineering of two-dimensional Fe-MOFs.
• In situ Fourier transform infrared and Raman spectroscopy during oxygen evolution reaction (OER).
• Electrochemical characterization for OER and hydrogen evolution reaction (HER) performance.

Main Results:

• Optimized Fe-MOF exhibited a change in Fe coordination number and formation of over 28% unsaturated Fe sites.
• In situ studies revealed oxidation of unsaturated Fe sites, water dissociation, and generation of *OH intermediates and Fe oxyhydroxide.
• Fe oxyhydroxide formation was found to be compatible with HER mechanisms, lowering energy barriers.

Conclusions:

• Defect engineering in Fe-MOFs facilitates controlled phase transformation to active Fe oxyhydroxide species.
• The optimized Fe-MOF electrocatalyst demonstrates excellent performance for both OER and HER.
• This work provides insights into the interplay between MOF structure, phase transformation, and electrocatalytic activity.