Permeate Flux Control of a Conductive Membrane through a PEDOT Redox Switch

A filtration membrane was modified with a conducting polymer coating for the permeate flux control through an electric input. The filtration membrane was first soaked in ferric chloride to load the oxidants on the membrane surface, followed by vapor-phase polymerization of 3,4-ethylenedioxythiophene (EDOT). Optimizations were carried out to balance the filtration performance and the electrical performance of the conductive membrane. Infrared spectroscopy and X-ray photoelectron spectroscopy confirmed the formation of PEDOT coatings on the membrane surfaces. Spectroelectrochemistry was carried out to confirm the reversible redox reactivity of the PEDOT coating when charged and discharged at +1 and −1 V. The permeate flux of the conductive membrane showed a switchable behavior during the PEDOT charging/discharging cycles. The swelling behavior of PEDOT coatings on the membrane in the charging/discharging cycle was confirmed by electrochemical atomic force microscopy with the ingress/egress of dopant ions being responsible for the membrane’s switchable flux properties. The reversible redox switching behavior of the conductive polymer coating on the filtration membrane provides a potential application for permeate flux control through an electric input.