Carbon dioxide (CO2) is currently considered as a waste material due to its negative impact on the environment. However, it is possible to create value from CO2 by capturing and utilizing it as a building block for commodity chemicals. Electrochemical conversion of CO2 has excellent potential for reducing greenhouse gas emissions and reaching the Paris agreement goal of zero net emissions by 2050. To date, carbon capture and utilization technologies (i.e., capture and conversion) have been studied mostly independently. In this communication, we report a methodology based on the integration of CO2 capture and conversion by the direct utilization of a CO2 capture media as the electrolyte for electrochemical conversion of CO2. This has a high potential for reducing capital and operational cost when compared to traditional methodologies (i.e., capture, desorption, and then utilization). A mixture of chemical and physical absorption solvents allowed for the captured CO2 to be converted to formate with faradaic efficiencies of up to 50% and with carbon conversion of ca. 30%. By increasing the temperature in the electrochemical reactor from 20 to 75 °C, the reaction rate toward formate increased by a factor of 10, reaching up to 0.7 mmol/m2·s. The direct conversion of captured CO2 was also demonstrated for carbon monoxide formation with faradaic efficiencies of up to 45%.

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.

Abstract: A continuous electrochemical process with integrated product separation has been developed for production of 2,5-furandicarboxylic acid (FDCA) by oxidation of 5-(hydroxymethyl)furfural (HMF) in aqueous alkaline media on non-noble Ni/NiOOH foam electrodes at ambient conditions. Initially, voltammetry studies were performed in both, acid and alkaline media, on various catalyst materials: Au, Au₃Pd₂, Pt, PbO₂, Ni/NiOOH and graphite. Preparative electrolysis was performed on Au, Au₃Pd₂, Pt, PbO₂, Ni/NiOOH electrodes in a divided glass cell and Ni/NiOOH showed the best performance with an FDCA yield of ≈ 90% and a Faradaic efficiency of ≈ 80%. The electrolysis conditions were then optimized to industrially relevant conditions in a filter-press type flow reactor with Ni/NiOOH foam anode. HMF concentrations as high as 10 wt% were converted to FDCA at pH 12 in a buffer free 0.1 M Na₂SO₄ electrolyte with continuous addition of NaOH to maintain constant pH. An FDCA separation yield up to 95% was achieved via pH shift crystallization. The electrolysis and FDCA separation results were used for the design and construction of a bench-scale system where continuous FDCA production, including integrated product separation, was tested and reported in this work. This publication for the first time presents a continuous electrochemical FDCA production system with integrated product separation at industrially relevant product concentrations, 10 wt% HMF, and utilizing non-noble electrode materials.