Inorganic and biocatalysts work together to reduce CO2

Advantages and disadvantages of electrocatalysis and biocatalysis

Methanol is one of the substances that we would like to obtain from climate-damaging CO₂. It is often used as a synthesis raw material in the chemical industry. "Many reduction steps are required to produce methanol, as carbon dioxide is the most highly oxidized form of carbon," explains Wolfgang Schuhmann. Electrocatalysis is able to initiate these steps. However, while it is still selective in the first step, the reaction path then branches out and up to 16 different products are formed, not necessarily methanol. The situation is different with biocatalysts: these natural enzymes catalyze just one reaction and therefore only yield one product. However, they are complicated to handle, very sensitive or require cofactors for the reaction.

Combining both processes

In order to combine the advantages of both processes, the team led by first authors Panpan Wang and Xin Wang married electrocatalysis and biocatalysis. While the first reaction step from CO₂ to formate is electrocatalytic, the second and third steps are catalyzed by formaldehyde dehydrogenase and alcohol dehydrogenase. These enzymes require NAD (nicotinamide adenine dinucleotide) as a cofactor, which is consumed by the catalytic reaction and must be regenerated. This regeneration is achieved by a third enzyme. Finally, the valuable substance methanol is produced. "The work proves that such hybrid cascades are in principle feasible and make complex, multi-step reactions selectively possible," summarizes Wolfgang Schuhmann.