Electrochemical processes are a promising technology for industrial production of chemicals. One of the major drawbacks of electrochemical systems is the low mass transfer of reactants toward the active surface area of the electrode. In this paper, an approach is presented to enhance the mass transfer and increase the overall performance of the reactions. The strategy comprises introduction of a pulsed electrolyte flow in the electrochemical flow cell. This pulsating behavior results in an improved mass transfer of electroactive species due to a higher instantaneous velocity driven by the pulsations. Though the net residence time of the reactants will not be altered due to the pulsation, the resulting enhancement of mass transfer leads to an increase of the conversion. The oxidation of 1,2-propanediol to lactic acid and pyruvic acid mediated by 4-Acetamido-(2,2,6,6-Tetramethylpiperidin-1-yl) oxidanyl (ACT-TEMPO) was chosen to study the influence of the pulsed flow. Under the pulsating regime, a yield increase of lactic acid of a factor of two and a 15-20% gain in selectivity to a total of 95% toward lactic acid can be achieved by tuning the process parameters.

In industrial electrochemical processes it is of paramount importance to achieve efficient, selective processes to produce valuable chemicals while minimizing the energy input. Although the electrochemical reduction of CO ₂ has received a lot of attention in the past decades, an economically feasible process has not yet been developed. Typically, the electrochemical reduction of CO ₂ is paired to water oxidation, forming oxygen, but an alternative strategy would be coupling the CO ₂ reduction reaction to an oxidation in which a higher-value product is co-produced, significantly improving the economic feasibility for CO ₂ reduction as a whole. Importantly, both reactions need to be chosen wisely to ensure their compatibility and to minimize the voltage requirements for the redox system. In this study, as an example of this approach, we demonstrate such a match: the electroreduction of CO ₂ to CO, paired with the electrooxidation of 1,2-propanediol to lactic acid. Combining these reactions decreases energy consumption by 35%, increases product value of the system, and results in combined faradaic efficiencies of up to 160% when compared to the CO ₂ reduction reaction in which oxygen is formed in the anode.