Anionic Ionomer: Released\nSurface-Immobilized Cations\nand an Established Hydrophobic Microenvironment for Efficient and\nDurable CO<sub>2</sub>‑to-Ethylene Electrosynthesis at High\nCurrent over One Month

Electrosynthesis of multicarbon products, such as C<sub>2</sub>H<sub>4</sub>, from CO<sub>2</sub> reduction on copper (Cu)\ncatalysts\nholds promise for achieving carbon neutrality. However, maintaining\na steady high current-level C<sub>2</sub>H<sub>4</sub> electrosynthesis\nstill encounters challenges, arising from unstable alkalinity and\ncarbonate precipitation caused by undesired ion migration at the cathode\nunder a repulsive electric field. To address these issues, we propose\na universal “charge release” concept by incorporating\ntiny amounts of an oppositely charged anionic ionomer (e.g., perfluorinated\nsulfonic acid, PFSA) into a cationic covalent organic framework on\nthe Cu surface (cCOF/PFSA). This strategy effectively releases the\nhidden positive charge within the cCOF, enhancing surface immobilization\nof cations to impede both outward migration of generated OH<sup>–</sup> and inward migration of cations, inhibiting carbonate precipitation\nand creating a strong alkaline microenvironment. Meanwhile, the ionomer’s\nhydrophobic chains create a hydrophobic environment within the cCOF,\nfacilitating efficient gas transport. In situ characterizations and\ntheoretical calculations demonstrate that the cCOF/PFSA catalyst establishes\na hydrophobic strong alkaline microenvironment, optimizing the adsorption\nstrength and configuration of *CO intermediates to promote the C<sub>2</sub>H<sub>4</sub> formation. The optimized catalyst achieves a\n70.5% Faradaic efficiency for C<sub>2</sub>H<sub>4</sub> with a partial\ncurrent density over 470 mA cm<sup>–2</sup>. Notably, it delivers\na high single-pass carbon efficiency of 96.5% for CO<sub>2</sub>RR\nand sustains an exceptional stability over 760 h. When implemented\nin a large-area MEA electrolyzer and a 5-cell MEA stack, the system\nachieves an industrial current of 15 A and continuous C<sub>2</sub>H<sub>4</sub> production exceeding 19 mL min<sup>–1</sup>,\nmarking a significant step toward industrial feasibility in CO<sub>2</sub>RR-to-C<sub>2</sub>H<sub>4</sub> conversion.