Enhancing the Performance of Layered Metal-Organic Framework Supercapacitors by Coordination Modulation

Gittins, Jamie W.; Balhatchet, Chloe J.; Fairclough, Simon M.; Forse, Alexander C.

doi:10.26434/chemrxiv-2022-m32fb

Cited by 2 publications

(6 citation statements)

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“…This finding supports the cation-dominated charging mechanism proposed from theoretical and experimental work for the related MOF Cu3(HHTP)2. 12,13 Therefore, whilst in-pore anion concentration was earlier shown to serve as a useful indicator of electrolyte-accessible pore volume and hence electrochemical performance (Figure 4e), the anions themselves are not primarily responsible for the charge storage in these systems.…”

Section: Ex-situ Nmr Charging Experimentsmentioning

confidence: 97%

“…Interestingly, the cation dominated nature of this charging mechanism is consistent with EQCM studies on the related MOF Cu3(HHTP)2 with 1 M NEt4BF4/ACN electrolyte. 13 The greater contribution of the cations compared to anions in charge storage of these systems suggests that the cation identity may be most closely linked to the overall electrochemical performance. Gittins et al previously demonstrated the impact of increasing the alkyl chain length in this family of cations, but further exploration of electrolytes is needed to improve electrochemical performance beyond that for 1 M NEt4BF4/ACN electrolyte.…”

Section: Operando Eqcm Experimentsmentioning

confidence: 99%

“…Electrochemical quartz crystal microbalance (EQCM) experiments were used to experimentally study the same MOF-electrolyte system employed in the QM/MM study above, Cu3(HHTP)2 with 1 M NEt4BF4/ACN, and supported the cation dominated nature of the charging mechanism. 13 More widely, He et al performed in-situ small-angle neutron scattering (SANS) experiments, on Ni3(HITP)2 cells with an organic electrolyte of sodium triflate in dimethylformamide (DMF). 14 The charging mechanism was found to be dependent on the electrode polarisation and the MOF was proposed to be ionophobic with respect to this electrolyte, with the pores devoid of electrolyte ions in the absence of an applied potential, a scenario which has been predicted to lead to improved performance in nanoporous carbon supercapacitors.…”

Section: Introductionmentioning

confidence: 99%

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Revealing Ion Adsorption and Charging Mechanisms in Layered Metal-Organic Framework Supercapacitors with Solid-State Nuclear Magnetic Resonance

Balhatchet,

Gittins,

Shin

et al. 2024

Preprint

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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 in conductive layered MOFs. To address this current lack of understanding of charge storage, 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 governed 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.

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Section: Ex-situ Nmr Charging Experimentsmentioning

confidence: 97%

Section: Operando Eqcm Experimentsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Revealing Ion Adsorption and Charging Mechanisms in Layered Metal-Organic Framework Supercapacitors with Solid-State Nuclear Magnetic Resonance

Balhatchet,

Gittins,

Shin

et al. 2024

Preprint

View full text Add to dashboard Cite

show abstract

Section: Ex-situ Nmr Charging Experimentsmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

Revealing Ion Adsorption and Charging Mechanisms in Layered Metal-Organic Framework Supercapacitors with Solid-State Nuclear Magnetic Resonance

Balhatchet,

Gittins,

Shin

et al. 2024

Preprint

View full text Add to dashboard Cite

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 governed 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.

show abstract

Enhancing the Performance of Layered Metal-Organic Framework Supercapacitors by Coordination Modulation

Cited by 2 publications

References 0 publications

Revealing Ion Adsorption and Charging Mechanisms in Layered Metal-Organic Framework Supercapacitors with Solid-State Nuclear Magnetic Resonance

Revealing Ion Adsorption and Charging Mechanisms in Layered Metal-Organic Framework Supercapacitors with Solid-State Nuclear Magnetic Resonance

Revealing Ion Adsorption and Charging Mechanisms in Layered Metal-Organic Framework Supercapacitors with Solid-State Nuclear Magnetic Resonance

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