A Flooding-Resistant Fluorinated Methacrylate Polymer for Enhanced CO₂ Electroreduction to Ethylene

The electrochemical reduction of CO₂ to ethylene offers a sustainable approach for the chemical industry and greenhouse gas mitigation. However, the widely used perfluorosulfonic acid (PFSA) binder is prone to causing catalyst layer flooding due to its excessive hydrophilicity and insufficient electro-wetting resistance. To address these limitations, we introduced a fluorinated methacrylate polymer (FMP), a low-cost hydrophobic film-forming agent commonly used for protective coatings on semiconductors, as a novel hydrophobic binder into the catalyst layer. Through multiple characterizations, we show that FMP, with its high fluorine content and absence of hydrophilic groups, imparts durable hydrophobicity and high electro-wetting resistance to the catalyst layer, thereby enhancing CO₂ transport while suppressing water accessibility. The incorporation of FMP into the catalyst layer enables enhanced CO₂ electroreduction performance in a membrane electrode assembly system. Compared to the conventional PFSA-based catalyst layer, the FMP-modified electrode delivers an enhanced ethylene Faradaic efficiency of 71.2% at a high current density of 400 mA cm^-2. Moreover, the electrode exhibits high operational durability, maintaining stable ethylene selectivity for over 50 h. The introduction of FMP effectively alleviates the long-standing flooding issue in CO₂ electroreduction.