Integrated CO₂ Capture and Conversion to Formate with a Molecular Platinum Bis(diphosphine) Electrocatalyst

Area of Science:

• Catalysis
• Electrochemistry
• Green Chemistry

Background:

• Carbon dioxide (CO2) is an abundant but dilute feedstock for valuable chemicals.
• Current CO2 utilization often involves energy-intensive capture, concentration, and regeneration steps.
• Integrated processes for direct CO2 reduction from sorbent-captured streams are highly desirable.

Purpose of the Study:

• To investigate the direct electrocatalytic reduction of sorbent-captured CO2.
• To develop an integrated process for CO2 utilization, avoiding separate concentration and regeneration steps.
• To elucidate the mechanism of CO2 reduction to formate.

Main Methods:

• Electrocatalytic reduction of 1,3-bis-(2,6-diisopropylphenyl)-imidazolium-2-carboxylate (IPr·CO2) using a [Pt-(dmpe)2]-(PF6)2 catalyst.
• Formation of IPr·CO2 from the reaction of sorbent 1,3-bis-(2,6-diisopropylphenyl)-imidazol-2-ylidene (IPr) with dilute CO2 streams.
• Kinetic studies and computational methods to explore the reaction mechanism and transition state.

Main Results:

• Quantitative formation of IPr·CO2 from dilute CO2 streams (10% and 0.04%).
• Electrocatalytic reduction of IPr·CO2 to formate with >70% Faradaic efficiencies.
• Phenol was identified as a proton source facilitating rapid CO2 release for reduction.
• Kinetic studies determined the rate of hydride transfer to be 0.22 M-1s-1.

Conclusions:

• Direct electrocatalytic reduction of sorbent-captured CO2 is feasible and efficient.
• The integrated process significantly simplifies CO2 utilization pathways.
• Understanding the hydride transfer mechanism provides insights for designing improved CO2 reduction catalysts.