(62e) Flow Electrolyser Mass Spectrometry Analysis (FEMS) of CO Electroreduction

The electrochemical reduction of CO₂ is a promising way to produce fuels and chemicals. However, CO₂ electroreduction currently suffers from poor selectivity and stability, and low energetic efficiency at practical reaction rates.To overcome some of the drawbacks and achieve a viable route for CO₂ reduction, the reaction should be split into a two-step process. Initially, CO₂ is reduced to CO which is followed by further reduction to the desired multi-carbons (e.g. C₂H₄, C₂H₅OH, etc.). Decoupling the process into two-steps allows for CO electrolysis in highly alkaline conditions, which enable enhanced efficiency. Prior works have shown progress towards understanding the impact of electrolyte ions, pH, mass transport, temperature, and pressure on the electrode activity and selectivity. To circumvent mass transport limitations, a gas diffusion electrode (GDE) has been incorporated into a flow cell reactor in order to facilitate better transport and distribution of reactants. A promising technique that can provide insight reaction information in real time is the flow electrolyser mass spectrometry (FEMS). This analytical technique collects volatile products of the reaction in the immediate vicinity of the electrode.

To exemplify the potential of FEMS, we studied the CO reduction on polycrystalline copper (pc-Cu). In addition, we placed great emphasis on the oxygen incorporation into ethanol, n-propanol, and acetaldehyde formation at high current electrolysis. We studied this crucial research question by examining C¹⁶O reduction in H₂¹⁸O electrolyte on pc-Cu electrocatalyst. In order to support our findings, we tested also reverse condition by studying C¹⁸O in H₂O electrolyte. Our experiments provide a strong evidence that acetaldehyde is formed from reactant oxygen. Solvent water affects the ethanol and n-propanol formation, but the oxygen exchange can be explained via isotopic scrambling of acetaldehyde.