CO2 Reduction in a Bio Mass-Paired Systems for the Production of e-Chemicals

Abstract

The electrification of chemical manufacturing is an important pathway toward reduced CO2 emissions. Direct electrochemical CO2 reduction can thereby become a key technology. CO2 electrolyzers produce cathodically platform chemicals as CO, format, ethanol or ethylene. The state-of-the-art anode process is the oxygen electro evolution which suffers from high over potentials and moderate valorization. An alternative is the anodic oxidation of biomass to valorized carbonaceous products, such as the oxidation of hydroxymethylfurfural (HMF) to the biopolymer precursor 2.5-furandicarboxylic acid (FDCA).In this work we report the design of electrolyzers flow cells with paired valorization of biomass and CO2. NiNC cathode GDEs are used for CO2 reduction to CO and NiFe-LDH anodes for the HMF oxidation in a zero-gap membrane electrolyzer flow cells. We used a bipolar membrane to separate and optimize either half-cell reactions. Inside the membrane, water is dissociated and the protons will neutralize carbonates on the cathode which is beneficial for a higher CO2 utilization and single pass. So, we can report close to 95% FE and 100% utilization efficiency towards CO.On the other hand, the hydroxide will stabilize the anode pH and enable PGM-free anodes compared to AEM CO2 electrolyzer. State-of-the-art HMF oxidation is a semi-batch setup, in which the HMF containing anolyte is recycled to complete HMF depletion and utilization. This design suffered from severe mass limitations. Therefore, we modified the semi-batch process into a continuous process and made tradeoffs between faradaic efficiency and utilization. As HMF is not stable in alkaline solutions we decided that a high utilization is beneficial because the intermediates are stable and could be recycled. We can report a single pass conversion of around 70 % towards FDCA at 200 mA cm-2 at a total utilization of 90%.Figure caption: Paired continuous HMF/CO2 electrolyzer with performance parameter. Figure 1