Flow Field\nDesign Matters for High Current Density\nZero-Gap CO<sub>2</sub> Electrolyzers

The commercialization of CO<sub>2</sub> electrolyzers\nrequires\nhigher current densities. This work demonstrates the necessity of\nflow field optimization for developing high-current-density CO<sub>2</sub> electrolyzers. Using three typical flow fields (serpentine,\nparallel, and interdigitated) as tools and combining multiple characterization\ntechniques, we investigated the principles for further flow field\noptimization. We recognized that optimizing the flow field involves\nmore than enhancing CO<sub>2</sub> distribution uniformity and ensuring\nno CO<sub>2</sub> starvation. It is also necessary to provide CO<sub>2</sub> flow-through transport while ensuring suppressed drainage\nbehavior. Optimizing based on this principle, we fabricated a multiserpentine\nflow field, and it realized a high CO selectivity of about 95% at\n0–350 mA cm<sup>–2</sup> with 0.1 M KHCO<sub>3</sub> and 50 °C cell temperature. Meanwhile, it achieves a high maximum\nCO partial current density of 409 mA cm<sup>–2</sup>, which\nis 43.5% higher than that of the conventional parallel flow field.