Abstract
Membrane materials with semipermeability for anions or for cations are of interest in electrochemical and nanofluidic separation and purification technologies. In this study, partially hydrolyzed polyacrylonitrile (phPAN) is investigated as a pH-switchable anion/cation conductor. When switching from anionic to cationic semipermeability, also the ionic current rectification effect switches for phPAN materials deposited asymmetrically onto a 5, 10, 20, or 40 μm diameter microhole in a 6 μm thick polyethylene-terephthalate (PET) film substrate. Therefore, ionic rectifier behavior can be tuned and used to monitor and characterize semipermeability. Effects of electrolyte type and concentration and pH (relative to the zeta potential at approximately 3.1) are investigated by voltammetry, chronoamperometry, and impedance spectroscopy. A computational model provides good qualitative agreement with the observed electrolyte concentration data. High rectification effects are observed for both cations (pH > 3.1) and anions (pH < 3.1) but only at relatively low ionic strengths.
| Original language | English |
|---|---|
| Pages (from-to) | 3214-3224 |
| Number of pages | 11 |
| Journal | ACS Applied Materials and Interfaces |
| Volume | 12 |
| Issue number | 2 |
| Early online date | 18 Dec 2019 |
| DOIs | |
| Publication status | Published - 15 Jan 2020 |
Funding
L.T. thanks the Global Excellence and Stature, University of Johannesburg for Doctoral Scholarship. DST/Mintek Nanotechnology Innovation Centre, University of Johannesburg, South Africa; the Water Research Commission, (grant number: K5/2567) South Africa; the National Research Foundation (CPRR grant numbers: 98887 and 118546), South Africa are acknowledged for their financial support. We thank Dr. Kyle C. Smith (University of Illinois) for helpful discussions.
Keywords
- double layer
- ion channel
- ion gating
- ionic rectifier
- membrane
- polyacrylonitrile
- steady state voltammetry
ASJC Scopus subject areas
- General Materials Science