Intrinsically Conductive and Cu-Functionalized Polymer-Composite Membranes as Gas Diffusion Electrodes for CO₂...

Area of Science:

• Electrochemistry
• Materials Science
• Chemical Engineering

Background:

• Gas diffusion electrodes (GDEs) are crucial for electrochemical carbon dioxide reduction (CO2RR).
• Controlling electrode architecture is key to optimizing CO2RR performance and selectivity.
• Existing GDEs often face challenges with pore wetting and limited control over active site distribution.

Purpose of the Study:

• To introduce a new class of GDEs with adjustable pore morphology.
• To investigate the impact of internal vs. external copper (Cu) active site distribution on CO2RR.
• To enhance selectivity towards C2 products in CO2RR.

Main Methods:

• Fabrication of intrinsically conductive polymer-composite membranes with controlled pore structures via film casting and phase separation.
• Selective functionalization of internal pore regions with copper (Cu) using a NaBH4-facilitated coating strategy.
• Testing of GDEs as free-standing cathodes in a CO2 flow electrolyzer.

Main Results:

• >70% Faradaic efficiencies for CO2RR products achieved at current densities up to 200 mA/cm².
• Internal Cu sites within the GDE pore system increased C2H4/CO selectivity by up to 3x compared to external Cu.
• Gaseous CO2 accessed internal Cu in macropores even after wetting, while CO2RR was suppressed in wetted nm-scale pores.

Conclusions:

• The novel GDEs with adjustable pore morphology and internal Cu active sites significantly enhance CO2RR selectivity.
• Controlling the location and accessibility of active sites within the GDE architecture is critical for efficient CO2 conversion.
• These findings offer a pathway for designing advanced electrodes for selective CO2 utilization.