Rationally Reconstructed Metal-Organic Frameworks as Robust Oxygen Evolution Electrocatalysts.

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Designing metal-organic frameworks (MOFs) for specific catalytic applications is an emerging field.
• The oxygen evolution reaction (OER) is crucial for energy conversion technologies but requires efficient electrocatalysts.
• Reconstructing MOF structures to tune active sites for enhanced OER performance has not been extensively explored.

Purpose of the Study:

• To report the first successful fabrication of a robust OER electrocatalyst via precision reconstruction of an MOF structure.
• To investigate the OER performance of a reconstructed MOF, MIL-53(Fe)-2OH, derived from MOF-74-Fe.
• To understand the electronic structure and reaction mechanisms responsible for the enhanced OER activity.

Main Methods:

• Precision reconstruction of MOF-74-Fe to yield MIL-53(Fe)-2OH.
• Electrochemical characterization, including overpotential, Tafel slope, and turnover frequency (TOF) measurements.
• Density functional theory (DFT) calculations and real-time kinetic simulations.

Main Results:

• The reconstructed MIL-53(Fe)-2OH catalyst exhibits significantly enhanced OER activity.
• Achieved a low overpotential of 215 mV at 10 mA cm⁻², a Tafel slope of 45.4 mV dec⁻¹, and a TOF of 1.44 s⁻¹.
• The catalyst's performance is over 80 times higher than commercial IrO₂, attributed to reduced crystal-field splitting and suppressed electron-hopping barriers.

Conclusions:

• Precision reconstruction of MOFs is a viable strategy for designing high-performance OER electrocatalysts.
• The electronic structure of MIL-53(Fe)-2OH, with reduced e_g-t_2g splitting and synergistic O species effects, guarantees efficient OER.
• The conversion from O* to OOH* is identified as the rate-determining step on the active sites of MIL-53(Fe)-2OH.