Lewis-Basic EDTA as a Highly Active Molecular Electrocatalyst for CO₂ Reduction to CH₄.

Area of Science:

• Electrochemistry and Catalysis
• Materials Science
• Computational Chemistry

Background:

• Heterogeneous Cu-based catalysts dominate CO2 hydrogenation but suffer from low selectivity due to complex active sites.
• Molecular catalysts offer precise control over active sites and structure for mechanism-based optimization.
• Efficient conversion of CO2 to valuable products like methane is crucial for sustainable energy.

Purpose of the Study:

• To develop a molecular catalyst for selective CO2 reduction to methane (CH4).
• To investigate the catalytic performance and mechanism of ethylenediaminetetraacetic acid (EDTA) immobilized on carbon nanotubes for CO2 reduction.
• To explore the structure-activity relationship for optimizing CO2 reduction reaction (CO2 RR) selectivity.

Main Methods:

• Immobilization of single ethylenediaminetetraacetic acid (EDTA) molecules on carbon nanotube surfaces.
• Electrochemical testing to evaluate catalytic performance, including Faradaic efficiency and partial current density.
• Density functional theory (DFT) calculations to elucidate reaction mechanisms and identify active sites.

Main Results:

• The immobilized EDTA catalyst achieved a high Faradaic efficiency of 61.6% for CH4 production.
• A partial current density of -16.5 mA cm⁻² was observed at -1.3 V vs. RHE, indicating excellent activity.
• DFT calculations identified Lewis basic COO⁻ groups in EDTA as active sites and revealed a favorable pathway for CH4 formation via *CO protonation.

Conclusions:

• Single EDTA molecules immobilized on carbon nanotubes serve as highly effective molecular catalysts for CO2 to CH4 conversion.
• The catalyst's high selectivity for CH4 is attributed to the specific energy barriers of reaction intermediates, particularly the facile protonation of *CO.
• This study provides a foundation for designing molecular catalysts with controlled selectivity for CO2 reduction reactions based on molecular structure.