Structure- and Potential-Dependent Cation Effects on CO Reduction at Copper Single-Crystal Electrodes.

Area of Science:

• Electrochemistry
• Catalysis
• Surface Science

Background:

• Electrocatalytic reduction of carbon monoxide (CO) to hydrocarbons is crucial for sustainable chemistry.
• Understanding the reaction mechanism and catalyst selectivity on copper electrodes is complex.
• Previous studies examined structural and electrolyte effects separately, lacking insight into cation influence on selectivity.

Purpose of the Study:

• To investigate the structure-sensitive cation effects on copper electrodes during CO electroreduction.
• To elucidate the influence of various alkaline cations (Li+, Na+, K+, Rb+, Cs+) on product selectivity (CH4 vs. C2H4) over a wide potential range.
• To understand the interplay between electrode structure, cation size, and applied potential in determining reaction pathways.

Main Methods:

• Electrochemical measurements on Cu(100), Cu(111), and polycrystalline copper electrodes.
• Online electrochemical mass spectrometry and high-performance liquid chromatography for product analysis.
• Fourier Transform infrared spectroscopy (FTIR) and density functional theory (DFT) for mechanistic insights.

Main Results:

• Cation effects on selectivity are potential-dependent: larger cations favor ethylene at higher potentials and methane at lower potentials.
• Cation effects are structure-sensitive: ethylene formation onset potential varies with electrode structure and cation size, unlike methane.
• FTIR and DFT studies indicate that cations facilitate CO dimer hydrogenation, favoring ethylene over methane at low overpotentials on Cu(100).

Conclusions:

• Potential-dependent and structure-sensitive cation effects can be leveraged to control selectivity in CO electroreduction.
• Alkaline cations play a critical role in stabilizing intermediates and influencing the rate-determining step (CO hydrogenation).
• This study provides a foundation for designing advanced copper-based catalysts for selective CO conversion to valuable hydrocarbons.