Capacitance-Tuning Guides the Electric Antifouling Membrane Design

Inrecent years, conductive membranes have attractedsignificantattention and have been extensively studied for their unique antifoulingmechanisms and regenerative properties. The current strategy primarilyfocuses on enhancing the conductivity of membranes. Yet, the resultingantifouling performance enhancement is limited due to lack of capacitance-tuning.Herein, we constructed hierarchical-nanostructure membrane carbonnanotubes-polyaniline-graphene quantum dots (CNT-PANI-GQDs),first demonstrating a capacitance-tuning strategy for enhancing themembrane's antifouling performance. PANI covers the CNTs'surface and cross-links them, forming a conductive 3D structure polymersubstrate. GQDs assisted with PANI are used for tuning the membranecapacitance. The CNT-PANI-GQDs had the highest capacitance among allthe membranes and exhibited the highest water flux, the best antifoulingperformance, and mechanical stability. Cross-flow filtration experimentswere conducted with the organic model foulants. After treating a 100ppm bovine serum albumin (BSA) solution with a voltage of -2.5V and running continuously for one h, the CNTs-PANI-GQDs membranemaintained a normalized flux of over 97%. Electrochemical measurementand Derjaguin-Landau-Verwey-Overbeek (DLVO) analysisrevealed that PANI and GQDs simultaneously enhance the pseudocapacitanceand double-layer capacitance, and the hierarchical nanostructure membranepossesses excellent charge transfer ability and a large electrochemicallyactive surface area. Increased capacitance leads to greater accumulationof surface charges and enhances the electrostatic repulsion againstimpurities. This work may offer valuable references to guide the designof electric antifouling membranes to favor water purification applications.