Steering CO₂ Electroreduction to Methane via Secondary-Sphere Noncovalent Interactions in NHC-Protected Copper...

Area of Science:

• Catalysis
• Materials Science
• Electrochemistry

Background:

• Copper catalysts show promise for CO2 reduction to hydrocarbons.
• Selective methane generation is hindered by competing pathways and poor active site control.

Purpose of the Study:

• To develop a ligand-microengineering strategy for synthesizing N-heterocyclic carbene (NHC)-protected Cu4O clusters.
• To enhance selectivity in CO2 electroreduction to methane (CH4).

Main Methods:

• Synthesis of NHC-protected Cu4O clusters using a green ball-milling approach.
• Electrochemical evaluation of catalyst performance, including Faradaic efficiency for CH4.
• In situ spectroscopy and density functional theory (DFT) calculations to understand reaction mechanisms.

Main Results:

• A series of NHC-protected Cu4O clusters were synthesized.
• Cluster 2c achieved an optimal CH4 Faradaic efficiency of 67.5% ± 2.1% at -1.4 V vs RHE.
• DFT calculations and spectroscopy revealed that secondary-sphere noncovalent interactions in 2c stabilize the *CHO intermediate, enhancing CH4 selectivity.

Conclusions:

• NHC ligands are advantageous for constructing stable and efficient copper cluster catalysts.
• Rational design of noncovalent interactions in the secondary coordination sphere can precisely steer CO2 electroreduction selectivity.
• This work establishes a new paradigm for controlling selectivity in CO2 reduction catalysis.