Local Proton Source in Electrocatalytic CO₂ Reduction with [Mn(bpy-R)(CO)₃ Br] Complexes

Area of Science:

• Inorganic Chemistry
• Electrochemistry
• Catalysis

Background:

• Manganese complexes are investigated for CO2 electroreduction.
• Understanding the influence of proton sources on catalytic mechanisms is crucial.

Purpose of the Study:

• To detail the electrochemical behavior and catalytic performance of fac-[Mn(pdbpy)(CO)3 Br] for CO2 reduction.
• To explore the impact of varying proton sources (water, TFE, phenol) on CO2 electroreduction selectivity.
• To compare the catalytic activity with a newly synthesized manganese complex, fac-[Mn(ptbpy)(CO)3 Br].

Main Methods:

• Preparative-scale electrolysis at -1.5 V vs SCE in CO2-saturated acetonitrile.
• Detailed spectroelectrochemical analysis (IR and UV/Vis) under inert and CO2 atmospheres.
• Comparative investigation of two related manganese catalysts with different ligand structures.

Main Results:

• Electrocatalytic CO2 reduction selectivity is highly sensitive to acid strength, affecting CO and formate yields.
• The manganese complex (1) exhibits suppressed dimer formation and an atypical reduction mechanism.
• Spectroscopic evidence confirms manganese hydride formation, indicating diverse electrocatalytic pathways.
• A second manganese complex (2) provides insights into the role of local proton sources.

Conclusions:

• The study elucidates the complex electrocatalytic CO2 reduction mechanism of manganese complexes.
• Acid strength and ligand design significantly influence catalyst performance and reaction pathways.
• The findings contribute to the development of efficient catalysts for CO2 conversion.