Enhancing Oxygen Evolution Reaction Performance of Metal-Organic Frameworks through Cathode Activation

Area of Science:

• Materials Science
• Electrochemistry
• Catalysis

Background:

• Metal-organic frameworks (MOFs) are promising electrocatalysts for the oxygen evolution reaction (OER) due to their active sites and porous structures.
• Challenges remain in developing MOF-based electrocatalysts with both high efficiency and excellent stability for OER.

Purpose of the Study:

• To investigate the efficacy of a cathodic activation strategy for enhancing the OER performance of M-HHTP (M = Ni, Cu, Co, Fe; HHTP = 2,3,6,7,10,11-hexahydroxytriphenylene).
• To explore the underlying mechanisms responsible for the performance improvements.

Main Methods:

• Cathodic activation treatment applied to M-HHTP materials.
• Electrochemical characterization including OER performance testing (overpotential, Tafel slope) and electrochemical impedance spectroscopy.
• Material characterization and density functional theory (DFT) calculations.

Main Results:

• Activated Ni-HHTP (HA-Ni-HHTP) exhibited excellent OER performance with a low overpotential of 140 mV at 20 mA cm⁻² and a Tafel slope of 78.7 mV⁻¹.
• Cathodic activation induced changes in semiconductor type, contact angle, and oxygen vacancy content, contributing to enhanced performance.
• Electrochemical impedance spectroscopy confirmed accelerated charge transport after activation, improving the OER process.

Conclusions:

• Cathodic activation is a viable strategy to significantly boost the OER electrocatalytic performance and stability of MOFs.
• The activated HA-Ni-HHTP surpasses commercial RuO₂ and rivals state-of-the-art MOF electrocatalysts.
• This activation strategy shows potential for improving the water oxidation performance of other MOFs, including Fe-HHTP, Co-HHTP, and Cu-HHTP.