Multifunctional Molecular Cages Boost Acidic CO₂ Electroreduction to Ethylene.

Area of Science:

• Electrochemistry
• Catalysis
• Materials Science
• Carbon Capture and Utilization

Background:

• Acidic electrocatalytic CO2 reduction (CO2RR) to multicarbon (C2+) products is promising for carbon utilization.
• Key limitations include Cu+ reduction to Cu0 and fast *CO intermediate diffusion, hindering C-C coupling and C2H4 selectivity.
• Acidic media enhance CO2 availability and suppress carbonate formation, making it ideal for CO2RR.

Purpose of the Study:

• To develop a strategy to stabilize Cu+ and restrict *CO diffusion for efficient C2H4 production in acidic CO2RR.
• To investigate the role of a molecular cage in enhancing C-C coupling kinetics and selectivity.
• To overcome intrinsic bottlenecks in acidic CO2RR for improved C2+ product formation.

Main Methods:

• Constructed a molecular cage on Cu2O surface by grafting cetyltrimethylammonium bromide (CTAB).
• Employed density functional theory (DFT) calculations to understand reaction mechanisms and energy barriers.
• Utilized *in situ* attenuated total reflection infrared spectroscopy (ATR-IR) and X-ray adsorption near-edge structure (XANES) to probe surface species and catalyst stability.

Main Results:

• The CTAB molecular cage stabilized Cu+ and restricted *CO diffusion, promoting C-C coupling.
• DFT calculations showed lowered C-C coupling energy barrier and raised hydrogen evolution barrier.
• Achieved 60% C2H4 Faradaic efficiency across a wide current density range (300-1100 mA cm-2) in strong acid.

Conclusions:

• The molecular cage strategy effectively overcomes limitations in acidic CO2RR, enhancing C2H4 selectivity.
• Demonstrated high CO2 single-pass utilization (64.7%), energy efficiency (37.9%), and long-term stability (>195 h).
• Presents a generalizable approach for designing catalysts for efficient acidic CO2 reduction to C2+ products.