Creating Bipolar Junction by Depositing Ultrathin Anion-Exchange Coating on CationExchange Membrane to Dissociate Water in Electrodialysis

Document Type : VSI: Membr. for Develop.&Sustain.

Authors

1 Department of Chemistry, Division of Science and Technology, University of Education, Lahore 44770, Pakistan

2 Department of Chemistry, Khwaja Fareed University of Engineering and Information Technology, Rahim Yar Khan, Pakistan

3 Department of Chemistry, University of Sahiwal, Sahiwal, Pakistan

4 Department of Chemistry, School of Natural Sciences, National University of Sciences and Technology, Islamabad, Pakistan

5 Department of Chemistry, Lahore Garrison University, DHA Phase VI, Lahore, Pakistan

6 Department of Chemistry, Kohsar University, Murree 47150, Punjab, Pakistan

Abstract

Ultrathin anion-exchange films have been created by employing layer-by-layer (LBL) deposition method. The LBL  deposited protonated poly(allylamine) (PAH)/poly(4-styrenesulfonate) (PSS) polyelectrolyte multilayers (PEMs) behave as  anionexchange films when PAH and PSS polyelectrolyte solutions are prepared in NaSCN as a supporting electrolyte (SE). Reflectance FTIR studies indicate that when PAH is prepared in 0.5 M NaSCN and PSS is prepared in 1 M NaSCN, the thickness of the film and the number of anion-exchange sites in the film are manifold greater than those in the film  fabricated from PAH and PSS polyelectrolytes when either of them is prepared in 0.5 M NaSCN. Transmembrane potential measurements were performed to measure the permselectivity of thus fabricated PEMs. These measurements indicate  that the fabricated films demonstrate high anion-exchange properties at neutral pH. However, the ion-exchange  character of the films switches from anions- to cations-exchange when pH of the surrounding solutions changes from 7  to 8.4. Diffusion dialysis results through the coated alumina membranes confirm such a change in the net charge of the  films with a change in the pH. Current density-voltage curve studies indicate plenty of formation of H+ and OHions  through water dissociation occurring at the interfacial bipolar junction created by depositing these anion-exchange  coatings on Nafion cation-exchange membrane (CEM). Donnan dialysis studies also indicate the formation of bipolar  junction through deposition of such films on cationexchange membranes. 

Graphical Abstract

Creating Bipolar Junction by Depositing Ultrathin Anion-Exchange Coating on CationExchange Membrane to Dissociate Water in Electrodialysis

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Volume 8, Issue 1
January 2022
  • Receive Date: 05 October 2021
  • Revise Date: 02 November 2021
  • Accept Date: 22 November 2021
  • First Publish Date: 22 November 2021