Cu⁺-Mediated CO Coordination for Promoting C-C Coupling for CO₂ and CO Electroreduction.

Area of Science:

• Electrochemistry
• Catalysis
• Materials Science

Background:

• Selective electrochemical conversion of carbon dioxide (CO2) to multicarbon (C2+) products is crucial for sustainable chemistry.
• The mechanism by which copper (Cu) oxidation states promote C-C coupling in CO2 reduction remains poorly understood, limiting catalyst design.

Purpose of the Study:

• To elucidate the role of Cu+ in promoting C-C coupling during electrochemical CO2 reduction.
• To investigate the stabilizing effect of iodide ions on Cu+ and its impact on C2+ selectivity.

Main Methods:

• Electrochemical CO2 reduction experiments using copper surfaces in bicarbonate electrolytes with and without iodide.
• In situ characterization to study the interaction between CO intermediates, Cu+, and iodide.
• Analysis of C2+ Faradaic efficiency and selectivity.

Main Results:

• Iodide ions accelerate the formation of Cu+ by promoting hydroxyl radical generation.
• Cu+ is stabilized by iodide via CuI formation, which binds CO intermediates.
• Formation of nonclassical Cu(CO)+ complexes on CuI sites significantly enhances C2+ selectivity (3.0-fold increase at -0.9 V RHE).
• Direct electroreduction of CO with CuI in iodide-containing electrolytes yields a 4.3-fold higher C2+ selectivity.

Conclusions:

• Cu+ plays a critical role in promoting C-C coupling for CO2 and CO electroreduction.
• Iodide stabilization of Cu+ is key to enhancing C2+ selectivity.
• This study provides mechanistic insights for designing efficient catalysts for CO2 upgrading.