Molecular Stabilization of Sub-Nanometer Cu Clusters for Selective CO₂ Electromethanation

Area of Science:

• Electrochemistry
• Materials Science
• Catalysis

Background:

• Electrochemical carbon dioxide (CO2) methanation is a key technology for CO2 utilization and renewable energy storage.
• Copper (Cu) nanoclusters are theoretically predicted to enhance methane selectivity in CO2 electroreduction.
• Previous methods using Cu-based metal-organic frameworks (MOFs) resulted in large Cu nanoparticles, favoring undesirable multi-carbon products.

Purpose of the Study:

• To develop an electrochemical oxidation-reduction method for preparing sub-nanometer Cu clusters from MOFs.
• To investigate the effect of Cu cluster size and stabilization on CO2 methanation selectivity.
• To offer a novel electrochemical approach for controlling product selectivity in Cu-catalyzed reactions.

Main Methods:

• Electrochemical oxidation-reduction of Cu-based MOFs to derive Cu clusters.
• Characterization using high-resolution microscopy (e.g., TEM, SEM).
• In situ and ex situ spectroscopic analyses (X-ray absorption spectroscopy, Raman spectroscopy) to understand material properties and reaction mechanisms.

Main Results:

• The derived Cu clusters achieved a faradaic efficiency of 51.2% for methane (CH4) production.
• A high partial current density of over 150 mA cm-2 was obtained for CH4.
• Sub-nanometer size and stabilization by residual MOF ligands were identified as key factors for high CH4 selectivity.

Conclusions:

• The electrochemical oxidation-reduction method successfully produced highly selective Cu nanoclusters for CO2 methanation.
• Sub-nanometer Cu cluster size and MOF ligand stabilization are crucial for steering selectivity towards methane.
• This work presents a new electrochemical strategy for precise control over Cu-based catalyst performance in CO2 conversion.