A 3D Numerical Study on Flow Field Designs in Zero-GapCO₂ Electrolyzers

The electrochemical CO₂ reduction reaction (CO₂RR) in a zero-gap electrolyzer is a promising pathway for carbon fixation via utilizing intermittent renewable energies to produce synthetic fuels and feedstocks, contributing to climate change mitigation. As a critical component of the electrolyzer, the flow field affects its performance by influencing the CO₂ transport. A 3D numerical model of the electrolyzer is critical for flow field optimization. However, numerical studies on the flow field in zero-gap electrolyzers are currently lacking. This study established a 3D model for CO₂ electrolyzers and validated it by experiments under acidic conditions. Based on this model, we investigated the effects of flow field designs on the performance of zero-gap electrolyzers. Two typical flow fields used in zero-gap CO₂ electrolyzers, including serpentine and parallel flow field designs, were evaluated, with the serpentine flow field demonstrating better CO₂ transport characteristics and performance. Then, the serpentine flow field was designed by further optimizing the channel-to-rib ratio and the channel depth within the flow field. The results indicate that a larger channel-to-rib ratio and shallower flow channels facilitate an increased average CO₂ flux and average CO₂ concentration within the catalyst layer. This research provides insights into flow field designs for zero-gap electrolyzers.