Processes associated with ionic current rectification at a 2D-titanate nanosheet deposit on a microhole poly (ethylene terephthalate) substrate

Films of titanate nanosheets (approx. 1.8-nm layer thickness and 200-nm size) having a lamellar structure can form electrolytefilled semi-permeable channels containing tetrabutylammonium cations. By evaporation of a colloidal solution, persistent deposits are readily formed with approx. 10 micromete...

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Bibliographic Details
Main Authors:	Putra, Budi Riza, Harito, Christian, Bavykin, Dmitry V, Walsh, Frank C, Wahyuni, Wulan Tri, Boswell, Jacob A, Squires, Adam M, Schmitt, Julien MF, Da Silva, Marcelo Alves, Edler, Karen J, Fletcher, Philip J, Gesell, Anne E, Marken, Frank
Format:	Journal Article
Language:	English
Published:	02-04-2020
Subjects:	Physics - Chemical Physics Physics - Materials Science
Online Access:	Get full text
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Summary:	Films of titanate nanosheets (approx. 1.8-nm layer thickness and 200-nm size) having a lamellar structure can form electrolytefilled semi-permeable channels containing tetrabutylammonium cations. By evaporation of a colloidal solution, persistent deposits are readily formed with approx. 10 micrometer thickness on a 6-micrometer-thick poly(ethylene-terephthalate) (PET) substrate with a 20 micrometer diameter microhole. When immersed in aqueous solution, the titanate nanosheets exhibit a p.z.c. of -37 mV, consistent with the formation of a cation conducting (semi-permeable) deposit. With a sufficiently low ionic strength in the aqueous electrolyte, ionic current rectification is observed (cationic diode behaviour). Currents can be dissected into (i) electrolyte cation transport, (ii) electrolyte anion transport and (iii) water heterolysis causing additional proton transport. For all types of electrolyte cations, a water heterolysis mechanism is observed. For Ca2+ and Mg2+ ions, water heterolysis causes ion current blocking, presumably due to localised hydroxide-induced precipitation processes. Aqueous NBu4+ is shown to invert the diode effect (from cationic to anionic diode). Potential for applications in desalination and/or ion sensing are discussed
DOI:	10.48550/arxiv.2004.01010