Direct Membrane Deposition for CO2 Electrolysis

The use of forward-bias bipolar membranes (f-BPM) in CO2 electrolyzers offers the advantage of avoiding costly CO2 reactant loss. However, current f-BPM-based electrolyzers require a high voltage and produce H2 at the expense of CO2 reduction products. In this work, we develop a direct membrane deposition (DMD) approach that combines anion and cation exchange membranes (AEM and CEM, respectively) to increase transport and facilitate CO2 regeneration. The DMD approach provides flexibility to tune the properties of the composite and optimize the AEM:CEM ratio for low resistance and low H2 evolution. Compared to a standard f-BPM, the DMD approach reduced the H2 Faradaic efficiency by 2-fold (25% vs 12%, respectively), reduced mass transport resistance by over 50%, decreased full-cell potential by 0.84 V, increased the selectivity toward multicarbon products by over 2-fold (29% vs 65%, respectively), and achieved >17% in multicarbon product energy efficiency at 300 mA cm–2.