Sulfur Changes the Electrochemical CO₂ Reduction Pathway over Cu Electrocatalysts

Area of Science:

• Electrochemistry
• Materials Science
• Catalysis

Background:

• Electrochemical CO2 reduction is a key strategy for mitigating carbon emissions and addressing energy demands.
• Copper-based electrocatalysts are known for producing multicarbon products like ethylene and ethanol from CO2.
• Selective CO2 reduction to formate remains a challenge for many catalytic systems.

Purpose of the Study:

• To develop novel electrocatalysts for selective electrochemical CO2 reduction.
• To investigate the mechanism of CO2 reduction to formate using sulfur-doped Cu2O.
• To understand the role of sulfur doping and surface reconstruction in enhancing formate selectivity.

Main Methods:

• Synthesis and characterization of sulfur-doped Cu2O electrocatalysts.
• Electrochemical CO2 reduction reaction (CO2 RR) measurements.
• In situ infrared absorption spectroscopy and Density Functional Theory (DFT) calculations.

Main Results:

• Sulfur-doped Cu2O electrocatalysts exclusively produce formate from CO2 reduction.
• In situ surface reconstruction generates active sulfur-adsorbed metallic Cu sites.
• DFT and spectroscopic data confirm promotion of the *OCHO intermediate and suppression of *H and *COOH adsorption.

Conclusions:

• Sulfur doping in Cu2O enables highly selective electrochemical CO2 reduction to formate.
• The dynamic S equilibrium and in situ surface reconstruction are crucial for catalytic activity and selectivity.
• This work provides a new pathway for efficient CO2 conversion to valuable formate.