Bipolar membranes for intrinsically stable and scalable CO₂ electrolysis

CO₂ electrolysis allows the sustainable production of carbon-based fuels and chemicals. However, state-of-the-art CO₂ electrolysers employing anion exchange membranes (AEMs) suffer from (bi)carbonate crossover, causing low CO₂ utilization and limiting anode choices to those based on precious metals. Here we argue that bipolar membranes (BPMs) could become the primary option for intrinsically stable and efficient CO₂ electrolysis without the use of scarce metals. Although both reverse- and forward-bias BPMs can inhibit CO₂ crossover, forward-bias BPMs fail to solve the rare-earth metals requirement at the anode. Unfortunately, reverse-bias BPM systems presently exhibit comparatively lower Faradaic efficiencies and higher cell voltages than AEM-based systems. We argue that these performance challenges can be overcome by focusing research on optimizing the catalyst, reaction microenvironment and alkali cation availability. Furthermore, BPMs can be improved by using thinner layers and a suitable water dissociation catalyst, thus alleviating core remaining challenges in CO₂ electrolysis to bring this technology to the industrial scale.