Hybrid Enzyme-Electrocatalyst Cascade Modified Gas-Diffusion Electrodes for Methanol Formation from Carbon Dioxide

Area of Science:

• Electrochemistry
• Biocatalysis
• Green Chemistry

Background:

• Carbon dioxide (CO2) reduction is crucial for sustainable chemical synthesis.
• Achieving high selectivity in CO2 electroreduction, particularly to valuable products like methanol, remains a challenge.
• Integrating bioelectrocatalysis offers a pathway to enhance selectivity and utilize milder reaction conditions.

Purpose of the Study:

• To develop a hybrid electrocatalytic-bioelectrocatalytic cascade for selective CO2 to methanol conversion.
• To integrate inorganic electrocatalysts with enzymatic cascades for efficient methanol synthesis.
• To establish a general strategy for improving selectivity in electrocatalytic CO2 reduction.

Main Methods:

• A gas diffusion electrode functionalized with Ag-Bi2O3 was used for initial CO2 to formate electroreduction.
• An enzymatic cascade involving formaldehyde dehydrogenase and alcohol dehydrogenase (both nicotinamide adenine dinucleotide [NAD]-dependent) further reduced formate.
• NAD+ regeneration was achieved electrochemically using diaphorase and a cobaltocene-based redox polymer.
• Methanol formation was verified using a biosensor incorporating alcohol oxidase and horseradish peroxidase.

Main Results:

• The hybrid system successfully converted CO2 to methanol through a selective reaction cascade.
• Ag-Bi2O3 demonstrated selective CO2 to formate reduction at neutral pH.
• The enzymatic cascade efficiently converted formate to methanol.
• Electrochemical regeneration of the NAD+ cofactor was successfully implemented.

Conclusions:

• The proposed hybrid electrocatalytic-bioelectrocatalytic cascade is a viable strategy for selective methanol production from CO2.
• This approach enhances the selectivity of electrocatalytic reactions and replaces sensitive bioelectrocatalytic steps with robust inorganic catalysts.
• The system offers a promising route for sustainable methanol synthesis and CO2 utilization.