Conversion of CO2 to formic acid in a microfluidic electrochemical cell with and without supporting electrolyte

Electrochemical reduction of carbon dioxide to formic acid or formate (FA) is considered an interesting route to valorize CO2 effluents. Here, we have performed the conversion of CO2 to FA in an undivided microchannel electrochemical reactor characterized by very small inter-electrode distances (75–250 μm) using Na2SO4 as supporting electrolyte (SE). It was found that the use of the microfluidic cell allows to work both in the presence and in the absence of SE with lower cell potentials with respect to conventional cells and to obtain significant conversions per pass of CO2 to FA. The effect of many parameters, such as distance between electrodes, flow rate, current density, concentration of Na2SO4 and pH, was studied. In particular, it was shown that the production of FA increases by reducing the concentrations of Na2SO4 and it presents the maximum value in the absence of it.