Selective Anion Anchoring in MOF-Based Supercapacitors Revealed with Operando Small-Angle X-Ray Scattering.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 41027923.
- Also identified by DOI 10.1038/s41467-025-63772-w and PMC identifier 12484562.
- Licence recorded as CC BY-NC-ND.
- Because redistribution is not established, this page shows the abstract only. Follow the links below for the full text.
Abstract
Understanding how ions interact with electrodes in electric double-layer capacitors (EDLCs) is key to advancing energy storage, yet many fundamental aspects remain unclear. Here, we employ operando small-angle X-ray scattering (SAXS) to investigate charge storage in metal-organic framework (MOF)-based supercapacitor electrodes as a model system. Using Ni<sub>3</sub>(2,3,6,7,10,11-hexaiminotriphenylene)<sub>2</sub> (Ni<sub>3</sub>(HITP)<sub>2</sub>) MOF electrodes and 1 M aqueous sodium bis(trifluoromethanesulfonyl)imide (NaTFSI) as the electrolyte, we show that TFSI<sup>-</sup> anions are immobilised near MOF pore walls via fluorine-hydrogen interactions with N-H functional groups of the MOF. We quantify the concentration of pinned anions and demonstrate that their immobilization persists across different applied cell voltages, resulting in a cation-dominated charge storage mechanism governed solely by Na<sup>+</sup> adsorption and desorption. Charge balancing is unaffected by whether voltage is applied stepwise or gradually, with no dynamic differences between in-pore and out-of-pore environments and no ion intercalation taking place.