Ni-Electrocatalytic CO₂ Reduction Toward Ethanol.

Area of Science:

• Electrochemistry
• Catalysis
• Materials Science

Background:

• Electrocatalytic CO2 reduction is key for sustainable synthetic fuel production.
• Copper-based catalysts are known for C2+ alcohol synthesis, but their mechanisms are complex.
• Developing efficient, selective, and well-understood catalysts remains a challenge.

Purpose of the Study:

• To develop a copper-free catalyst for selective CO2 reduction to C2+ alcohols.
• To elucidate the C-C coupling mechanism in CO2 reduction on a novel NiO catalyst.
• To understand how catalyst structure influences reaction pathways and selectivity.

Main Methods:

• Synthesis of a highly mesoporous NiO catalyst via block copolymer microphase separation.
• Electrochemical CO2 reduction experiments to determine Faradaic efficiency and selectivity.
• C1-feeding experiments, in situ spectroscopy, and theoretical calculations to probe reaction mechanisms.
• Analysis of catalyst structure and surface properties.

Main Results:

• A Cu-free, mesoporous NiO catalyst achieved 75.2% Faradaic efficiency for ethanol production at -0.6 V vs RHE.
• The catalyst's mesoporous structure created a CO2-rich, H2O-deficient interface, suppressing hydrogen evolution.
• Direct coupling of *CO2 and *COOH was identified as the C-C bond formation pathway on NiO, distinct from Cu-based mechanisms.
• Subsequent reduction via *COCOH and *OC2H5 intermediates was found to be energetically favorable.

Conclusions:

• The reported NiO catalyst offers a highly selective, Cu-free alternative for CO2 to ethanol conversion.
• The study reveals an unconventional C-C coupling mechanism on NiO, driven by strong CO2 adsorption.
• This work provides fundamental insights into C-C coupling for C2+ synthesis and opens new avenues for catalyst design.