Inversed Cation Size Effects on Methanol Formations From CO₂ Electroreduction by Immobilized Cobalt Phthalocyanine

Area of Science:

• Electrochemistry
• Catalysis
• Sustainable Energy

Background:

• Electrocatalytic reduction of carbon dioxide (CO2) to methanol is a key sustainable fuel synthesis route.
• Cation effects in the electric double layer (EDL) are crucial for catalytic performance, but their influence on methanol synthesis is less understood than CO2-to-CO conversion.

Purpose of the Study:

• To investigate the influence of cations in the EDL on the electrocatalytic reduction of CO2 to methanol using immobilized cobalt phthalocyanine (CoPc).
• To elucidate the kinetic mechanisms and cation-dependent trends in methanol synthesis.

Main Methods:

• Multiscale simulation was employed to model the electrocatalytic process.
• Analysis focused on the rate-determining step (RDS) of methanol formation.

Main Results:

• Methanol synthesis over CoPc is kinetically governed by the final proton transfer step.
• The EDL environment significantly accelerates this RDS.
• Catalytic activity shows a clear dependence on cation radius: Li+ > Na+ > K+ > Cs+.
• Smaller cations lower the proton transfer barrier due to enhanced accessibility and tighter coordination, providing greater electrostatic stabilization.

Conclusions:

• Smaller cations enhance methanol synthesis rates by lowering the RDS barrier.
• However, smaller cations can also hinder OH- transfer, indicating a balance between kinetic promotion and mass transfer limitations.
• Cation choice is a critical factor for optimizing electrocatalytic methanol production.