Ion-selective transport in surface-modified cellulose membranes for aqueous ionic thermoelectrics

Ashokan, Anjali; Rahme, Kamil; Palanisamy, Rupa Ranjani; Padmanathan, N.; Razeeb, Kafil M.; Biswas, Subhajit; Holmes, Justin D.

Ion-selective transport in surface-modified cellulose membranes for aqueous ionic thermoelectrics

dc.contributor.author	Ashokan, Anjali	en
dc.contributor.author	Rahme, Kamil	en
dc.contributor.author	Palanisamy, Rupa Ranjani	en
dc.contributor.author	Padmanathan, N.	en
dc.contributor.author	Razeeb, Kafil M.	en
dc.contributor.author	Biswas, Subhajit	en
dc.contributor.author	Holmes, Justin D.	en
dc.contributor.funder	Higher Education Authority	en
dc.contributor.funder	Horizon 2020	en
dc.date.accessioned	2025-12-01T16:46:16Z
dc.date.available	2025-12-01T16:46:16Z
dc.date.issued	2025-09-02	en
dc.description.abstract	Efficient recovery of low-grade heat (≤100 °C) remains a significant challenge in sustainable energy conversion. Here, we report a strategy to enhance ionic thermoelectric performance in biocompatible regenerated cellulose (RC) membranes by tailoring their surface charge. Surface functionalisation was achieved using two oppositely charged organic moieties: 2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPO) to introduce carboxyl groups, and 3-chloro-2-hydroxypropyltrimethylammonium chloride (CHMAC) to graft quaternary ammonium functionalities. This work presents the first direct, side-by-side comparison of oppositely charged surface functional groups, carboxyl (TEMPO) and quaternary ammonium (CHMAC), on ionic thermoelectric behaviour in cellulose membranes. These modifications significantly increased the fixed surface charge density, promoting ion selectivity and enabling efficient ion transport under a thermal gradient. CHMAC-functionalised RC membranes exhibited the highest performance, with a Seebeck coefficient of +6.1 mV K−1 in a stacked membrane configuration using 0.1 mM HCl electrolyte, representing a tenfold enhancement compared to unmodified RC membranes. Correspondingly, ionic conductivity increased by up to 950-fold, with an ionic thermoelectric power factor of 1.38 μW m−1 K−2. This study establishes a clear link between surface charge engineering and thermodiffusion-enhanced ionic transport in RC membranes, offering a scalable and sustainable route for harvesting low-grade thermal energy using green, aqueous systems.	en
dc.description.sponsorship	Irish Government (DAFM NXTGENWOOD research program, grant agreement: 2019PROG704); European Union's Horizon 2020 research and innovation programme (Grant no. 964251 (TRANSLATE))	en
dc.description.status	Peer reviewed	en
dc.description.version	Published Version	en
dc.format.mimetype	application/pdf	en
dc.identifier.citation	Ashokan, A., Rahme, K., Palanisamy, R.R., Padmanathan, N., Razeeb, K.M., Biswas, S. and Holmes, J.D. (2025) 'Ion-selective transport in surface-modified cellulose membranes for aqueous ionic thermoelectrics', Journal of Materials Chemistry A, 13(39), pp. 33671–33684. https://doi.org/10.1039/D5TA05281E	en
dc.identifier.doi	10.1039/D5TA05281E	en
dc.identifier.endpage	33684	en
dc.identifier.issued	39	en
dc.identifier.journaltitle	Journal of Materials Chemistry A	en
dc.identifier.startpage	33671	en
dc.identifier.uri	https://hdl.handle.net/10468/18329
dc.identifier.volume	13	en
dc.language.iso	en	en
dc.publisher	Royal Society of Chemistry (RSC)	en
dc.rights	© 2025, The Royal Society of Chemistry.	en
dc.rights.uri	https://creativecommons.org/licenses/by/3.0/	en
dc.subject	Efficient recovery of low-grade heat	en
dc.subject	Sustainable energy conversion	en
dc.subject	Ionic thermoelectric performance	en
dc.title	Ion-selective transport in surface-modified cellulose membranes for aqueous ionic thermoelectrics	en
dc.type	Article (peer-reviewed)	en