Dynamic Relocation of Copper Catalysts in Gas Diffusion Electrodes during CO₂ Electroreduction

Area of Science:

• Electrochemistry
• Materials Science
• Catalysis

Background:

• Developing technologies for CO2 conversion using renewable energy is crucial.
• Copper (Cu) is a key electrocatalyst for converting CO2 into multicarbon (C2+) products.
• Understanding Cu catalyst behavior in gas diffusion electrodes (GDEs) at high current densities is vital for industrial applications.

Purpose of the Study:

• To investigate the correlation between Cu catalyst structure, chemical state, and C2+ selectivity in Cu-GDEs during CO2 reduction reactions (CO2RR).
• To examine catalyst behavior at industrially relevant current densities (>200 mA/cm2).

Main Methods:

• Utilized ex situ and in situ scanning X-ray fluorescence microscopy to observe Cu relocation.
• Employed in situ X-ray absorption spectroscopy to identify chemical states (Cu1+).
• Used online gas chromatography to monitor product selectivity and identify degradation mechanisms.

Main Results:

• Significant Cu relocation within the GDE was observed after CO2RR.
• Cu relocation occurs via a pH-dependent dissolution-redeposition mechanism, more pronounced at high pH.
• Electrode flooding was identified as the primary cause for decreased C2+ selectivity over time, overshadowing Cu relocation effects.

Conclusions:

• Cu relocation in GDEs is pH-dependent and occurs through dissolution-redeposition.
• Electrode flooding is the main limitation for sustained C2+ selectivity in Cu-GDEs at high current densities.
• Findings offer insights for designing stable and selective Cu-based GDEs for CO2 electrolyzers.