In the last decade, there has been increasing research interest in the electrochemical conversion of glycerol, mainly due to the growing global biodiesel production (71.5 million t in 2024), which produces large quantities of relatively pure glycerol as a byproduct (45-80%). Partial oxidation of glycerol can result in the production of a wide range of industrial feedstocks. One possible conversion method is electrochemical oxidation, which has the primary advantage of being carried out under mild conditions (room temperature, atmospheric pressure).

At present, the energy requirement of carbon dioxide electrolyzer cells is still relatively high due to the necessary cell voltage. This can be overcome by replacing this reaction with alternative anode processes, such as the electrochemical oxidation of glycerol (GOR). On the one hand, this offers the possibility of lowering the cell voltages and, on the other hand, it converts a material currently treated as waste into a valuable chemical feedstock.

In our work, OER was replaced by the GOR using carbon supported Pt nanoparticles as anode catalyst, while the reduction of CO₂ to CO was carried out on Ag catalyst in a continuous flow microfluidic electrolysis cell. We have explored how the glycerol oxidation activity and selectivity of the catalyst depend on the catalyst layer composition (ionomer quality and quantity), glycerol concentration, electrolyte flow rate and applied anode potential. Nearly 100% of the charge passed was converted to carbon monoxide evolution at the cathode, which was not affected by the presence of glycerol and glycerol oxidation products. Glycerol oxidation products in the liquid phase were identified as glycerate, dihydroxyacetone, glycolate, tartronate, oxalate, formate and lactate by NMR spectroscopy and high performance liquid chromatography. The long-term stability of the CO2RR/GOR process was investigated by potentiostatic measurements. A gradual decrease in current density was observed when the potential was maintained at a certain value, which was linked to the gradual oxidation of the platinum surface by GOR products. The activity of the catalyst can be preserved by periodically reducing the Pt surface. Using this dynamic electrochemical protocol, the activity (current densities above 200 mA cm^-2) and selectivity of the anode catalyst can be preserved.