Fast Catalysis at Low Overpotential: Designing Efficient Dicationic Re(bpy²⁺)(CO)₃I Electrocatalysts for CO₂...

Area of Science:

• Inorganic Chemistry
• Electrochemistry
• Catalysis

Background:

• Rhenium polypyridyl complexes are investigated for CO2 electroreduction.
• Tuning complex structure can optimize catalytic performance.

Purpose of the Study:

• To synthesize and characterize dicationic Re(bpy)(CO)3I complexes with varying cation positions.
• To evaluate the impact of cationic group placement on electrocatalytic CO2 reduction efficiency and mechanism.

Main Methods:

• Electrochemical synthesis and characterization of rhenium complexes.
• Electrocatalytic CO2 reduction studies in CH3CN/H2O mixtures.
• Kinetic analysis to determine reaction rates and overpotentials.

Main Results:

• A series of isomeric dicationic Re(bpy)(CO)3I complexes were synthesized.
• The placement of cationic pendants resulted in an ~800-fold increase in catalytic rate.
• Optimized isomers showed enhanced CO2 adduct stabilization and lowered activation energy for C-OH bond cleavage.

Conclusions:

• Subtle structural modifications, specifically cation positioning, dramatically influence electrocatalytic CO2 reduction.
• Coulombic stabilization and transition state stabilization are key factors for rate acceleration.
• Optimized complexes facilitate a low overpotential 'protonation-first' pathway.