Mechanism of CO₂ Electrolysis with Heterogenized Molecular Iridium Catalysts Deciphered Using Operando Spectroscopy

Area of Science:

• Electrochemistry
• Catalysis
• Materials Science

Background:

• Understanding the mechanism of electrochemical CO2 reduction is vital for developing efficient catalysts.
• Current proposed mechanisms often lack direct experimental evidence, relying heavily on computational studies.
• Heterogenized molecular catalysts offer advantages but present challenges in mechanistic elucidation.

Purpose of the Study:

• To experimentally elucidate the reaction mechanism of electrochemical CO2 reduction to formic acid using a heterogenized iridium catalyst.
• To correlate experimental observations with computational data for a more robust understanding.
• To demonstrate the utility of multioperando analysis for studying complex catalytic systems.

Main Methods:

• Multioperando analysis combining gas diffusion electrodes (GDEs) with a heterogenized iridium catalyst.
• Operando X-ray absorption fine structure (XAFS) spectroscopy to track electronic and intermediate structural changes.
• Operando surface-enhanced Raman scattering (SERS) to monitor real-time catalytic intermediates.

Main Results:

• Three distinct iridium intermediates were identified during the electrochemical reduction of CO2 to formic acid.
• The temporal appearance of these intermediates strongly correlated with DFT-calculated activation energies.
• Experimental validation of a heterogenized catalytic mechanism was achieved, overcoming typical challenges.

Conclusions:

• The study provides the first experimental corroboration of a detailed reaction mechanism for heterogenized iridium-catalyzed CO2 reduction.
• This work establishes a powerful multioperando approach for investigating complex catalytic processes.
• The findings pave the way for the rational design of improved catalysts for CO2 conversion.