Capacitance-Tuning Guides the Electric Antifouling Membrane Design

In recent years, conductive membranes have attracted significant attention and have been extensively studied for their unique antifouling mechanisms and regenerative properties. The current strategy primarily focuses on enhancing the conductivity of membranes. Yet, the resulting antifouling performance enhancement is limited due to lack of capacitance-tuning. Herein, we constructed hierarchical-nanostructure membrane carbon nanotubes–polyaniline–graphene quantum dots (CNT-PANI-GQDs), first demonstrating a capacitance-tuning strategy for enhancing the membrane's antifouling performance. PANI covers the CNTs' surface and cross-links them, forming a conductive 3D structure polymer substrate. GQDs assisted with PANI are used for tuning the membrane capacitance. The CNT-PANI-GQDs had the highest capacitance among all the membranes and exhibited the highest water flux, the best antifouling performance, and mechanical stability. Cross-flow filtration experiments were conducted with the organic model foulants. After treating a 100 ppm bovine serum albumin (BSA) solution with a voltage of −2.5 V and running continuously for one h, the CNTs-PANI-GQDs membrane maintained a normalized flux of over 97%. Electrochemical measurement and Derjaguin–Landau–Verwey–Overbeek (DLVO) analysis revealed that PANI and GQDs simultaneously enhance the pseudocapacitance and double-layer capacitance, and the hierarchical nanostructure membrane possesses excellent charge transfer ability and a large electrochemically active surface area. Increased capacitance leads to greater accumulation of surface charges and enhances the electrostatic repulsion against impurities. This work may offer valuable references to guide the design of electric antifouling membranes to favor water purification applications.