Direct Membrane Deposition for CO₂ Electrolysis

Abstract

The use of forward-bias bipolar membranes (f-BPM) in CO 2 electrolyzers offers the advantage of avoiding costly CO 2 reactant loss. However, current f-BPM-based electrolyzers require a high voltage and produce H 2 at the expense of CO 2 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 CO 2 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 .