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 H-2 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 H-2 evolution. Compared to a standard f-BPM, the DMD approach reduced the H-2 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).