Synergistic Microphase Separation and Interfacial Microenvironment Regulation in Fluorinated Polybenzimidazole Membranes for Efficient Electrocatalytic CO 2 Reduction

ABSTRACT Anion exchange membrane (AEM) with high ion conductivity and effective interfacial regulation is crucial for electrocatalytic CO 2 reduction (ECR). Herein, we design a fluorinated polybenzimidazole (6FPBI) grafted with both piperidinium and trimethylammonium cations to fabricate a high‐performance AEM. Benefiting from ether‐free fluorinated backbone and dual cation group, 6FPBI‐TP membrane exhibits IEC of 3.63 mmol g − 1 , suppressed water uptake of 50.44%, and suppressed swelling ratio (9.26%), alongside a tensile strength of 19.14 MPa. The 6FPBI‐TP membrane exhibits a competitive OH − conductivity of 142.75 mS cm − 1 at 80°C and an elevated selectivity of 67%. Its moderately hydrophobic, positively charged surface optimizes the three‐phase catalytic microenvironment, mitigating water flooding and suppressing the hydrogen evolution side reaction. In membrane electrode assembly, 6FPBI‐TP membrane delivers FE CO of 94.4% at 150 mA cm − 2 , exceeding OPBI‐TP membrane (89.1%). 6FPBI‐TP membrane maintains stable electrolysis over 100 h, while OPBI‐TP membrane fails after only 25 h. Molecular dynamics simulations reveal a dominant vehicular OH − transport pathway and enhanced alkaline stability derived from ether‐free fluorinated backbone. This dual cationic strategy not only constructs well‐defined ion transport channels but also modulates the interfacial microenvironment, thereby affording a straightforward route to AEM with high stability and high selectivity for ECR.