Revealing Ion Adsorption and Charging Mechanisms in Layered Metal–Organic Framework Supercapacitors with Solid-State Nuclear Magnetic Resonance
Year: 2024
Type: article
Abstract: Conductive layered metal-organic frameworks (MOFs) have demonstrated promising electrochemical performances as supercapacitor electrode materials. The well-defined chemical structures of these crystalline porous electrodes facilitate structure-performance studies, however there is a fundamental lack in the molecular-level understanding of charge storage mechanisms in conductive layered MOFs. To address this, we employ solid-state nuclear magnetic resonance (NMR) spectroscopy to study ion adsorption in nickel 2,3,6,7,10,11-hexaiminotriphenylene, Ni3(HITP)2. In this system, we find that separate resonances can be observed for the MOF’s in-pore and ex-pore ions. The chemical shift of in-pore electrolyte is found to be dominated by specific chemical interactions with the MOF functional groups, with this result supported by quantum-mechanics/molecular-mechanics (QM/MM) and density functional theory (DFT) calculations. Quantification of the electrolyte environments by NMR was also found to provide a proxy for electrochemical performance, which could facilitate the rapid screening of synthesised MOF samples. Finally, the charge storage mechanism was explored using a combination of ex-situ NMR and operando electrochemical quartz-crystal microbalance (EQCM) experiments. These measurements revealed that cations are the dominant contributor to charge storage in Ni3(HITP)2, with anions contributing only a minor contribution to the charge storage. Overall, this work establishes the methods for studying MOF-electrolyte interactions via NMR spectroscopy. Understanding how these interactions influence the charging storage mechanism will aid the design of MOF-electrolyte combinations to optimise the performance of supercapacitors, as well as other electrochemical devices including electrocatalysts and sensors.
DOI: 10.1021/jacs.4c05330
Institutions: University of Cambridge, Imperial College London, Thomas Young Centre, Centre National de la Recherche Scientifique, Université Toulouse III - Paul Sabatier, Centre Interuniversitaire de Recherche et d’Ingénierie des Matériaux, University of California, Berkeley, Réseau sur le Stockage Electrochimique de l'énergie
Language: English
Field: Materials Science
Domain: Physical Sciences
Open Access status: hybrid
Estimated APC paid: $4,500
Funders: UK Research and Innovation, Leverhulme Trust, University of Cambridge, Agence Nationale de la Recherche, Cambridge Trust, China Scholarship Council, Ministry of Minority Affairs, HORIZON EUROPE Framework Programme, Engineering and Physical Sciences Research Council, European Research Council, H2020 European Research Council, HORIZON EUROPE European Research Council
Awards: G2214117044, Materials Chemistry HEC Consortium (MCC), Supercharging Metal-Organic Frameworks (SuperMOF), G354711118, G3761587124, G4283178789, G6060081955, Disruptive Modes and Materials of Energy Storage, Transforming Supercapacitors by using Metal-Organic Framework Electrodes, G8713401677, G955821083
OpenAlex ID: W4401512222