Overcoming Mass Transport Limitations in Electrochemical Reactors with a Pulsating Flow Electrolyzer

Abstract

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.

Bipotentiostatic tandem electrocatalysis of the CO2 reduction reaction yielding C2+ fuels

“…The pulsed potential program we adopted here is a well-known method that possibly suppresses the HER through periodic anodic potential application with a small amount of charge. 10,37 This experimental design provided better reproducibility in the CO2RR and excluded the biased comprehension of the specific catalysts.…”

“…accordance with electrode mass transport theory. 32,[37][38][39]48 All subsequent discussions hereon regarding the bipotentiostatic CO2RR are on experiments performed with electrode configurations employing WE2 with a rectangular central opening mirroring WE1 dimensions.…”

“…S9 and S31†), the best results were obtained when the size of the central opening was equivalent to the area of WE1, in accordance with electrode mass transport theory. 32,37–39,48 All subsequent discussions hereon regarding the bipotentiostatic CO2RR are on experiments performed with electrode configurations employing WE2 with a rectangular central opening mirroring WE1 dimensions.…”

“…Rather than using the synthesized Cu catalysts, we used the commercial Cu mesh as an electrocatalyst and a modulated potential application method (see S19 †). The pulsed potential program we adopted here is a well-known method that possibly suppresses the HER through periodic anodic potential application with a small amount of charge 10,37. This experimental design provided better reproducibility in the CO2RR and excluded the biased comprehension of the specific catalysts.…”

Analysis of the Reactive CO2 Surface Flux in Electrocatalytic Aqueous Flow Reactors

“…The electrochemical reduction of CO 2 in aqueous flow reactors is emerging as an especially attractive route to recycle carbon. − Despite continued performance improvements, however, the central questions surrounding transport of the dissolved gases to the reactive surface still remain unresolved. Indeed, overcoming mass transport limitations has been a central focus of many recent reactor engineering and design efforts. − …”