Efficient Methane Electrosynthesis Enabled by Tuning Local CO₂ Availability.

Area of Science:

• Electrochemistry
• Catalysis
• Renewable Energy Storage

Background:

• Carbon dioxide electroreduction (CO2RR) is a key technology for storing intermittent renewable electricity.
• Methane produced via CO2RR can serve as a carbon-neutral fuel and feedstock, leveraging existing infrastructure.
• Current CO2RR to methane methods face challenges with low selectivity at high current densities.

Purpose of the Study:

• To investigate methods for improving methane selectivity in CO2RR at commercially relevant current densities.
• To understand the role of CO2 coverage on copper catalysts in methane generation pathways.
• To develop an experimental strategy for efficient methane electrosynthesis using dilute CO2.

Main Methods:

• Density functional theory (DFT) calculations to model CO2 coverage effects on copper surfaces.
• Experimental control of local CO2 availability by adjusting gas stream concentration.
• Electrochemical reactions regulated by current density to optimize methane production.

Main Results:

• Lowering CO2 coverage on copper surfaces was found to favor methane generation intermediates over C-C coupling.
• Achieved a methane Faradaic efficiency (FE) of 48% at a partial current density of 108 mA cm-2.
• Demonstrated stable methane electrosynthesis for 22 hours using a dilute CO2 gas stream.

Conclusions:

• Controlling local CO2 availability on copper catalysts is crucial for enhancing methane selectivity in CO2RR.
• The developed strategy enables efficient methane production from dilute CO2 feedstocks.
• This research provides a viable pathway for producing methane with high FE and conversion rates, utilizing renewable energy.