Relative Insignificance of Polyamide Layer Selectivity for Seawater Electrolysis Applications

Xuechen Zhou, Le Shi, Rachel Taylor, Chenghan Xie, Bin Bian, Cristian Picioreanu, Bruce Logan

Research output: Contribution to journalArticlepeer-review

Abstract

Low-cost polyamide thin-film composite (TFC) membranes are being explored as alternatives to cation exchange membranes for seawater electrolysis. An optimal membrane should have a low electrical resistance to minimize applied potentials needed for water electrolysis and be able to block chloride ions present in a seawater catholyte from reaching the anode. The largest energy loss associated with a TFC membrane was the Nernstian overpotential of 0.74 V (equivalent to 37 Ω cm2 at 20 mA cm-2), derived from the pH difference between the anolyte and catholyte and not the membrane ohmic overpotential. Based on analysis using electrochemical impedance spectroscopy, the pristine TFC membrane contributed only 5.00 Ω cm2 to the ohmic resistance. Removing the polyester support layer reduced the resistance by 79% to only 1.04 Ω cm2, without altering the salt ion transport between the electrolytes. Enlarging the pore size (∼5 times) in the polyamide active layer minimally impacted counterion transport across the membrane during electrolysis, but it increased the total concentration of chloride transported by 60%. Overall, this study suggests that TFC membranes with thinner but mechanically strong supporting layers and size-selective active layers should reduce energy consumption and the potential for chlorine generation for seawater electrolyzers.
Original languageEnglish (US)
JournalEnvironmental Science & Technology
DOIs
StatePublished - Sep 18 2023

ASJC Scopus subject areas

  • Environmental Chemistry
  • Chemistry(all)

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