Engineering Bimetal Synergistic Electrocatalysts Based on Metal-Organic Frameworks for Efficient Oxygen Evolution.

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Metal-organic frameworks (MOFs) offer tunable structures for electrochemical applications.
• MOFs often exhibit poor stability in alkaline media, necessitating investigation into their transformation products.
• Understanding the active species in MOFs during reactions is crucial for catalyst design.

Purpose of the Study:

• To investigate the in situ transformation of MOFs in alkaline solution during the oxygen evolution reaction (OER).
• To identify the active catalytic species derived from MOFs for OER.
• To elucidate the reaction mechanism of MOF-derived catalysts in OER.

Main Methods:

• Synthesis of mixed Ni-MOFs and Fe-MOFs via sonication.
• Electrochemical testing of MOFs as catalysts for OER in alkaline electrolyte.
• Characterization of in situ generated species using ex situ transmission electron microscopy (TEM) and X-ray diffraction (XRD).

Main Results:

• MOFs undergo ligand/ionic exchange in alkaline solution, transforming into bimetallic hydroxide species.
• In situ generated NiFe-LDH acts as the primary active component for OER.
• The optimized catalyst (FN-2) demonstrated a low overpotential of 275 mV at 10 mA cm⁻² and sustained activity for 100 hours.

Conclusions:

• The active species in MOF electrocatalysts for OER in alkaline media are often in situ generated layered double hydroxides.
• This transformation mechanism provides insights into MOF stability and catalytic activity.
• The findings contribute to a deeper understanding of MOF-based electrocatalysts for efficient oxygen evolution.