From overlooked to outstanding: a molecular silver complex in heterogeneous CO₂ electroreduction

Area of Science:

• Electrochemistry
• Catalysis
• Materials Science

Background:

• Molecular transition metal complexes, particularly silver-based ones, are effective catalysts for electrochemical CO2 reduction (eCO2R).
• Heterogenization of molecular catalysts can improve their performance and stability.

Purpose of the Study:

• To investigate the application of a silver dithiacyclam polymer (Ag(dithiacyclam)) for eCO2R in both homogeneous and heterogeneous systems.
• To optimize the heterogenization process for enhanced catalytic activity and selectivity.

Main Methods:

• Synthesis and application of a silver dithiacyclam polymer catalyst.
• Heterogenization of the catalyst onto a gas diffusion electrode (GDE).
• Testing in a zero-gap electrolyzer (ZGE) at various current densities.
• Ink engineering and dispersion solvent optimization for GDE fabrication.

Main Results:

• The heterogenized Ag(dithiacyclam) catalyst on a GDE showed significantly improved eCO2R performance compared to the homogeneous system.
• A CO selectivity (FECO) of 97% was achieved at 50 mA cm-2.
• Optimization of GDE fabrication yielded FECO up to 90% at 300 mA cm-2.
• High eCO2R performance was maintained at 500 mA cm-2, with FECO of 55%, outcompeting hydrogen evolution.

Conclusions:

• Heterogenization of molecular silver catalysts onto GDEs is a highly effective strategy for boosting electrochemical CO2 reduction.
• Optimized GDE fabrication is crucial for achieving high performance at industrially relevant current densities.
• Molecular systems can serve as excellent precursors for highly active heterogeneous catalysts for CO2 conversion.