Molecularly Designed Cathode for Copper-Benzimidazole-Induced CO₂ Reduction to MeOH

Area of Science:

• Electrochemistry
• Catalysis
• Sustainable Chemistry

Background:

• Electrochemical reduction of carbon dioxide (CO₂) is crucial for developing a circular economy.
• Significant progress has been made in CO₂ conversion to carbon monoxide (CO) and formic acid.
• Efficiently producing more reduced, energy-dense products like methanol (MeOH) via sustainable routes remains a challenge.

Purpose of the Study:

• To report a novel molecular electrode for the direct six-electron reduction of CO₂ to methanol.
• To investigate a sustainable pathway for methanol synthesis using water as a proton source.
• To elucidate the catalytic mechanism and electrode stability for CO₂ conversion.

Main Methods:

• Design and synthesis of a molecular electrode featuring a copper-hydride center and benzimidazole-hydride units.
• Electrochemical reduction experiments to convert CO₂ to methanol.
• Density Functional Theory (DFT) investigations to determine the reaction mechanism.
• Electron microscopy to evaluate electrode morphology and stability before and after electrolysis.

Main Results:

• Achieved a global Faradaic efficiency (FE_G) of 22% for CO₂ reduction.
• Obtained a methanol (MeOH) product selectivity of 61%.
• Identified a formato pathway for methanol generation, supported by DFT calculations and experimental observations (concurrent formic acid formation, absence of formaldehyde).

Conclusions:

• The developed molecular electrode enables direct six-electron reduction of CO₂ to methanol with significant selectivity.
• The study provides a mechanistic understanding of the catalytic process, highlighting the role of hydride transfer.
• The electrode demonstrates stability over 12 hours of electrolysis, indicating potential for scalable applications in CO₂ valorization.