Bio-inspired bimetallic models for electrochemical CO₂ reduction.

Area of Science:

• Electrochemistry
• Organometallic Chemistry
• Catalysis

Background:

• The carbon monoxide dehydrogenase (CODH) enzyme utilizes a bimetallic active site for synergistic catalysis of CO2/CO interconversion.
• Developing artificial systems that mimic CODH active sites is crucial for efficient CO2 reduction.
• Lewis acid assistance is a potential strategy to enhance CO2 reduction reactions.

Purpose of the Study:

• To design and synthesize rhenium dipyridine derivatives incorporating a Lewis acid moiety (KN18C6) for CO2 reduction.
• To investigate the effect of the KN18C6 moiety on electrode deposition and CO2 reduction reaction (CO2RR) performance.
• To understand the mechanism of electrode deposition and its impact on catalytic activity.

Main Methods:

• Synthesis of rhenium dipyridine derivatives with varying linker flexibility to the KN18C6 moiety.
• Electrochemical characterization including cyclic voltammetry and chronoamperometry.
• Infrared spectroelectrochemistry (IR-SEC) and control experiments to elucidate deposition mechanism.

Main Results:

• The developed rhenium complexes exhibit strong electrode deposition under CO2 in the presence of potassium cations.
• Deposition rate correlates with the flexibility of the linkage between the rhenium framework and the KN18C6 moiety; more flexible linkers lead to faster deposition.
• While deposition enhances CO2RR initiation, it unfortunately inhibits the subsequent C-O bond cleavage step.

Conclusions:

• Rhenium dipyridine derivatives functionalized with KN18C6 can effectively promote electrode deposition during CO2RR.
• Linker flexibility is a key factor controlling the deposition rate, offering a design parameter for catalyst immobilization.
• The observed deposition, while beneficial for initial CO2 activation, poses a challenge for complete CO2 conversion by hindering C-O bond cleavage.