Microfluidic devices for the sequential reduction of CO2. – MF-CO2

We inspired from the litterature to design electrochemical flow cells. They are made of replaceable working and counter electrodes, thus allowing to test different materials and catalysts in the same cell. We have also developped an online detection system based on a micro gas chromatograph and an electrolyte circulation system. We have formulated an ink containing a cobalt-based macrocyclic catalysts, which we then deposited on the working electrode used in the cell.

We are now able to determine the product distribution of electrocatalysts performing the CO2 reduction reaction under a continuous flow of electrolyte. Thanks to this system, we have shown that the cobalt-based catalyst that we are using can produce carbon monoxide, but also light hydrocarbons in smaller amounts.

The performances of the catalyst in a single reactor will be study in more detail using NMR and gas chromatography, in order to determine the reaction products a s a function of catalytic conditions. We will then move to sequential reactions using several catalysts (identical or different ones) in series.

An article is currently being prepared, which described the results obtained concerning the reduction of CO2 by a cobalt-based catalyst under circulating conditions.

Carbon dioxide (CO2) is a major exhaust product of transportation and industrial processes in industrial societies. The deleterious effect of this gas on our environment is becoming a serious concern, but our societies remain dependent on fossil fuels as one of their main energy source. The transformation of this by-product into added-value chemicals or energy-rich fuels is a highly interesting valorization route, both from environmental and industrial perspectives.


In this context, the electrochemical reduction of CO2 is an interesting approach, which allows synthesizing simple molecules such as methanol or formaldehyde or more complex ones such as butanol. These chemicals can be used either as building blocks for commodity chemicals or directly as fuels. Although a lot of research has been done in the last years to improve them, catalytic CO2 reduction reactions suffer from one of the two following problems:

i) Low selectivity: metallic copper, for example, has been largely studied for its ability to reduce CO2 electrochemically in aqueous media. This catalyst is appreciated for the variety of compounds it can produce: CO, CH4, C2H4, HCOOH. Despite the progresses made over the last years to improve its selectivity, it is not satisfactory yet, with 4 to 5 major products (representing at least 10% each of the total products) and no simple way of separating them.

ii) The formation of low added value products: several molecular catalysts (rhenium bipyridine/CO or manganese bipyridine/CO complexes, iron porphyrins) are efficient for the electrochemical or photochemical reduction of CO2, but their only product is carbon monoxide, which added value or energetic potential is quite low.

To circumvent these issues, we propose to develop microfluidic systems that will feature successive electrocatalytic reactors in order to perform CO2 reduction reactions sequentially. Our bet is that a series of well-controlled cascade reactions is more efficient and easier to handle than trying to optimize a single catalyst for the synthesis of added-value hydrocarbons all at once. These systems will allow optimizing independent catalysts for a given reaction involving CO2 or its reduction products. Once the catalytic conditions of each single microreactor will be optimized, they will be incorporated in complex, multi-step reaction schemes. The use of microfluidic systems will allow controlling the availability of substrate independently for each catalyst and also offer parallelization possibilities, which can speed up the optimization of catalytic conditions.
Because of its industrial significance and its synthetic versatility (in particular the presence of and electrophilic carbon), our main target is formaldehyde. This synthetic building block will be obtained by the electrochemical reduction of CO2 into CO in aqueous medium and the subsequent electrocatalytic reduction of CO into formaldehyde in acidic medium. We will use well known and commercially available catalysts for each of these steps, which will be set in the microreactors developed in the course of the project. Specific microfluidic tools will also be developed for the detection of reaction products and parameters optimization.


This project proposes to demonstrate the feasibility of sequential multi-step electrosynthetic reactions applied to the reduction of CO2. Its completion will showcase the benefits of microfluidic in electrosynthetic reactions by the control it allows on the availability and circulation of reactants and products. The knowledge and the microfluidic electrosynthetic devices developed along this project will be applied to other reactions involving CO2 and will benefit the entire community interested in such reactions.