Electroreduction of CO₂ to CO Paired with 1,2-Propanediol Oxidation to Lactic Acid. Toward an Economically Feasible System

Abstract

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 CO2 has received a lot of attention in the last decades, an economically feasible process has not yet been developed. Typically, the electrochemical reduction of CO2 is paired to water oxidation, forming oxygen, but an alternative strategy would be coupling the CO2 reduction reaction to an oxidation in which a higher-value product is co-produced, significantly improving the economic feasibility for CO2 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 CO2 to CO, paired with the electrooxidation of 1,2-propanediol to lactic acid. Combining these reactions decreases energy consumption by ca. 35%, increases of product value of the system, and results in combined faradaic efficiencies of up to 160% when compared to the CO2 reduction reaction in which oxygen is formed in the anode.

Recent Advances on Electrolysis for Simultaneous Generation of Valuable Chemicals at both Anode and Cathode

“…save 1.25-times cost while AEM was used in a paired configuration at the same time. [90] Furthermore, Houache et al took glycerol electro-oxidation into consideration, achieving CO 2 RR and glycerol oxidation coelectrolysis. The CO was obtained from CO 2 RR over commercial Ag electrode, while formate was simultaneously gained from GOR with their as-prepared carbon supported Ni 1−x M x (M = Bi, Pd, and Au) electrocatalyst.…”

“…Copyright 2019, Wiley-VCH. d,e) Reproduced with permission [90]. Copyright 2019, American Chemical Society.…”

Prospects of Value‐Added Chemicals and Hydrogen via Electrolysis

“…The concept of combining different anodic and cathodic important reactions can go beyond hydrogen production. Synthesis of CO via CO 2 electroreduction concomitant with production of lactic acid via 1,2‐propanediol electrooxidation was recently reported, highlighting the increased interest of the scientific community for generating new alternative processes based on renewable energy.…”

A brief review of electrocatalytic reduction of CO2—Materials, reaction conditions, and devices

“…Its large overpotential and low product value are the intrinsic weaknesses of this reaction. Instead of applying appropriate catalysts to promote OER, alternative strategies have been proposed in replacing it with other oxidation reactions, mitigating overpotentials, and producing value‐added chemicals 134‐138 . Bevilacqua et al 137 combined CO 2 reduction and ethanol oxidation to acetate at cathode and anode (Figure 10B), respectively, providing a low working potential and hence a reduced energy consumption in contrast to the cell with OER, from 130 to 77 kWh.…”