In alkaline and neutral MEA CO₂ electrolyzers, CO₂ rapidly converts to (bi)carbonate, imposing a significant energy penalty arising from separating CO₂ from the anode gas outlets. Here we report a CO₂ electrolyzer uses a bipolar membrane (BPM) to convert (bi)carbonate back to CO₂, preventing crossover; and that surpasses the single-pass utilization (SPU) limit (25% for multi-carbon products, C₂₊) suffered by previous neutral-media electrolyzers. We employ a stationary unbuffered catholyte layer between BPM and cathode to promote C₂₊ products while ensuring that (bi)carbonate is converted back, in situ, to CO₂ near the cathode. We develop a model that enables the design of the catholyte layer, finding that limiting the diffusion path length of reverted CO₂ to ~10 μm balances the CO₂ diffusion flux with the regeneration rate. We report a single-pass CO₂ utilization of 78%, which lowers the energy associated with downstream separation of CO₂ by 10× compared with past systems.

在碱性和中性MEA CO ₂电解槽中，CO ₂快速转化为碳酸氢盐，从阳极气体出口分离CO ₂造成显着的能量损失。在这里，我们报道了一种 CO ₂电解槽，它使用双极膜 (BPM) 将碳酸氢盐转化回 CO ₂ ，​​从而防止交叉；并且超过了之前中性介质电解槽的单程利用率 (SPU) 限制（多碳产品 C ₂₊为 25%）。我们在 BPM 和阴极之间采用固定的无缓冲阴极电解液层来促进 C ₂₊产物，同时确保碳酸氢盐在阴极附近原位转化回 CO ₂ 。我们开发了一个能够设计阴极电解液层的模型，发现将还原的CO ₂的扩散路径长度限制在~10 μm 可以平衡CO ₂扩散通量与再生速率。我们报告单程 CO ₂利用率为 78%，与过去的系统相比，与下游 CO ₂分离相关的能量降低了 10 倍。