Electrocatalytic Reduction of CO₂

Converting carbon dioxide into valuable chemical fuels such as formic acid, methanol or long-chain alcohols can effectively combat problems such as global warming and fossil resource shortages. The reduction reaction of carbon dioxide by electrocatalysis is a very promising strategy. Finding efficient, safe, and highly selective electrocatalysts for CO₂ reduction reactions is an important task. Transition metal complexes are common catalysts used for electrocatalytic CO₂ reduction. This is mainly because they have two advantages. First, in the reduction process of metal complexes, there will be an empty coordination point conducive to the coordination and activation of CO₂. Secondly, through the modification of ligands, the electronic and geometric structures of metal complexes can be changed, thereby regulating the catalytic activity of catalysts. Currently, most of the transition metal complexes, such as Re, Ru, Fe, Co, Ni, Mn, have been widely used in the electrocatalytic reduction of CO₂.

Basic steps

The electrocatalytic reduction of CO₂ by transition metal complexes generally uses heterogeneous catalysis, that is, the reaction occurs at the interface between the electrode and the electrolyte.

• The reduction process consists of the following three steps:

(1) CO₂ is chemically adsorbed on the transition metal complex to activate CO₂.

(2) The activated CO₂ obtains electrons or protons (or simultaneously), the C-O bond breaks and/or forms a C-H bond to form a reaction intermediate (e.g., *COOH).

(3) Continue to obtain electrons to form the final product and then separate from the transition metal complex, the catalytic site enters the next reaction cycle.

• The reaction equation of CO₂ electrocatalytic reduction to other products is as follows:

Application

Transition metal complexes are good electron transport mediators and exhibit a variety of chemical properties. It has been reported in the early 1980s that cobalt-based macrocyclic complexes can effectively electro catalyze CO₂ reduction to produce CO, HCOOH, methanol and methane, whether in solution or adsorbed on carbon electrodes. Shen's group ^[1] immobilized co-protoporphyrin molecular catalysts in pure electrolyte aqueous solution on pyrolytic graphite (PG) electrode and used electrocatalytic reduction to reduce CO₂ to CO and methane, in addition to small amounts of HCOOH and methanol were produced. In addition to cobalt-based complexes, other transition metal complexes such as ruthenium, copper, palladium, and nickel are also irreplaceable for the electrocatalytic reduction of CO₂.

Figure 1. Mechanistic scheme for the electrochemical reduction of CO₂ on Co protoporphyrin

What can we do?

Alfa Chemistry has a profound research foundation in the field of electrocatalytic reduction of CO₂ by transition metal complexes, and is committed to the goal of reducing CO₂ emissions. Alfa Chemistry will serve you with the most abundant experience and the most affordable price. If you have any problems, we will provide technical support for you. If you have special needs, we will develop a unique solution for you. Please don't hesitate to contact us.

Reference

• Shen, J.; et al. Electrocatalytic reduction of carbon dioxide to carbon monoxide and methane at an immobilized cobalt protoporphyrin. Nature Communications. 2015, 6.