Efficient multicarbon formation in acidic CO₂ reduction via tandem electrocatalysis

Area of Science:

• Electrochemistry
• Catalysis
• Materials Science
• Chemical Engineering

Background:

• Electrochemical reduction of carbon dioxide (CO2) in acidic media offers high single-pass carbon efficiency.
• Hydrogen evolution reaction (HER) competes with CO2 reduction, lowering selectivity.
• Multicarbon (C2+) product formation requires CO generation and subsequent C-C coupling, needing distinct catalyst properties.

Purpose of the Study:

• To decouple the CO2-to-C2+ reaction into two distinct steps: CO2-to-CO and CO-to-C2+.
• To develop a tandem catalyst system with two layers to achieve high selectivity and efficiency in CO2 electroreduction.
• To overcome the challenge of achieving distinct catalyst properties required for CO2 reduction and C-C coupling in a single catalyst.

Main Methods:

• Designed a two-layer tandem electrode system.
• The first layer utilized atomically dispersed cobalt phthalocyanine for selective CO2 to CO reduction.
• The second layer employed a Cu nanocatalyst with a Cu-ionomer interface for enhanced C-C coupling.

Main Results:

• The tandem electrode achieved 61% C2H4 and 82% C2+ Faradaic efficiency at 800 mA cm−2.
• Optimized for single-pass utilization, the system demonstrated 90% ± 3% single-pass carbon efficiency.
• Simultaneously achieved 55% ± 3% C2H4 and 76% ± 2% C2+ Faradaic efficiency at 800 mA cm−2 with a CO2 flow rate of 2 ml min−1.

Conclusions:

• Decoupling the CO2-to-C2+ reaction into sequential steps using a tandem catalyst is an effective strategy.
• The atomically dispersed cobalt phthalocyanine and Cu nanocatalyst system significantly enhances selectivity and efficiency.
• This approach enables high single-pass carbon efficiency and substantial C2+ product yields for CO2 electroreduction.