In Situ NMR Spectroscopy of Supercapacitors: Insight into the Charge Storage Mechanism

Electrochemical capacitors, commonly known as supercapacitors, are important energy storage devices with high power capabilities and long cycle lives. Here we report the development and application of in situ nuclear magnetic resonance(NMR) methodologies to study changes at the electrode−electrolyte interface in working devices as they charge and discharge. For a supercapacitor comprising activated carbon electrodes and an organic electrolyte, NMR experiments carried out at different charge states allow quantification of the number of charge storing species and show that there are at least two distinct charge storage regimes. At cell voltages below 0.75 V, electrolyte anions are increasingly desorbed from the carbon micropores at the negative electrode, while at the positive electrode there is little change in the number of anions that are adsorbed as the voltage is increased. However, above a cell voltage of 0.75 V, dramatic increases in the amount of adsorbed anions in the positive electrode are observed while anions continue to be desorbed at the negative electrode. NMR experiments with simultaneous cyclic voltammetry show that supercapacitor charging causes marked changes to the local environments of charge storing species, with periodic changes of their chemical shift observed. NMR calculations on a model carbon fragment show that the addition and removal of electrons from a delocalized system should lead to considerable increases in the nucleus-independent chemical shift of nearby species, in agreement with our experimental observations

Increased Cycling Cell Numbers and Stem Cell Associated Proteins as Potential Biomarkers for High Grade Human Papillomavirus+ve Pre-Neoplastic Cervical Disease

High risk (oncogenic) human papillomavirus (HPV) infection causes cervical cancer. Infections are common but most clear naturally. Persistent infection can progress to cancer. Pre-neoplastic disease (cervical intraepithelial neoplasia/CIN) is classified by histology (CIN1-3) according to severity. Cervical abnormalities are screened for by cytology and/or detection of high risk HPV but both methods are imperfect for prediction of which women need treatment. There is a need to understand the host virus interactions that lead to different disease outcomes and to develop biomarker tests for accurate triage of infected women. As cancer is increasingly presumed to develop from proliferative, tumour initiating, cancer stem cells (CSCs), and as other oncogenic viruses induce stem cell associated gene expression, we evaluated whether presence of mRNA (detected by qRT-PCR) or proteins (detected by flow cytometry and antibody based proteomic microarray) from stem cell associated genes and/or increased cell proliferation (detected by flow cytometry) could be detected in well-characterised, routinely collected cervical samples from high risk HPV+ve women. Both cytology and histology results were available for most samples with moderate to high grade abnormality. We found that stem cell associated proteins including human chorionic gonadotropin, the oncogene TP63 and the transcription factor SOX2 were upregulated in samples from women with CIN3 and that the stem cell related, cell surface, protein podocalyxin was detectable on cells in samples from a subset of women with CIN3. SOX2, TP63 and human gonadotrophin mRNAs were upregulated in high grade disease. Immunohistochemistry showed that SOX2 and TP63 proteins clearly delineated tumour cells in invasive squamous cervical cancer. Samples from women with CIN3 showed increased proliferating cells. We believe that these markers may be of use to develop triage tests for women with high grade cervical abnormality to distinguish those who may progress to cancer from those who may be treated more conservatively

Solvent-derived defects suppress adsorption in MOF-74

Acknowledgements: This work is financially supported by National Natural Science Foundation of China (21922410, 22072133, 22275159, X.K.); Zhejiang Provincial Natural Science Foundation (LR19B050001, X.K.); Leading Innovation and Entrepreneurship Team of Zhejiang Province (2020R01003, X.K.); CEA ECC program (Programme Economie Circulaire du Carbone-Projet HyperCool NMR, G.D.P.), the French National Research Agency (CBH-EUR-GS and ARCANE ANR-17-EURE-0003, G.D.P.), the “Investissements d’avenir” program (ANR-15-IDEX-02, CDP-DefiCO2, G.D.P.) and the European Research Council Grant ERC-CoG-2015 (No. 682895, G.D.P.). US Department of Energy (DoE), Office of Science, Office of Basic Energy Sciences under award number (DE-SC0019992, J.R.L. and J.A.R.).AbstractDefects in metal-organic frameworks (MOFs) have great impact on their nano-scale structure and physiochemical properties. However, isolated defects are easily concealed when the frameworks are interrogated by typical characterization methods. In this work, we unveil the presence of solvent-derived formate defects in MOF-74, an important class of MOFs with open metal sites. With multi-dimensional solid-state nuclear magnetic resonance (NMR) investigations, we uncover the ligand substitution role of formate and its chemical origin from decomposed N,N-dimethylformamide (DMF) solvent. The placement and coordination structure of formate defects are determined by 13C NMR and density functional theory (DFT) calculations. The extra metal-oxygen bonds with formates partially eliminate open metal sites and lead to a quantitative decrease of N2 and CO2 adsorption with respect to the defect concentration. In-situ NMR analysis and molecular simulations of CO2 dynamics elaborate the adsorption mechanisms in defective MOF-74. Our study establishes comprehensive strategies to search, elucidate and manipulate defects in MOFs.</jats:p

Income security during public health emergencies: the COVID-19 poverty trap in Vietnam.

The COVID-19 poverty trap is shaped by barriers to accessing prevention, vulnerability to economic disruption and financial uncertainties, and incurrence of catastrophic costs as people try to cope with the outbreak. To ensure socioeconomic stability and confidence during public health crises and in the long run, social protection schemes (e.g. social insurance, microfinancing) must be in place to help people cope with the loss of income security and reduced confidence in society

Research data supporting "Insights into the electric double-layer capacitance of two-dimensional electrically conductive metal-organic frameworks"

This data is primarily related to the synthesis and characterisation of Cu₃(HHTP)₂, and its electrochemical characterisation in symmetric electric double-layer capacitors with 1 M NEt₄BF₄ in acetonitrile electrolyte. The data provided here consists of: - CIF Files (contains information of the CIF files used during modelling and simulations. These can also be found at: https://doi.org/10.5281/zenodo.4694845). - Conductivity Measurement Data (contains results from the measurements used to calculate conductivity values). - Electrochemistry Data (contains CV data from 3-electrode cells; CV, GCD, EIS, and long-term cycling stability data from composite Cu₃(HHTP)₂ EDLCs with 1 M NEt₄BF₄ in acetonitrile electrolyte; CV, GCD, and EIS data from a Cu₃(HHTP)₂ EDLCs with 1 M NEt₄BF₄ in acetonitrile electrolyte; characterisation data for a YP50F EDLC with 1 M NEt₄BF₄ in acetonitrile; and characterisation data for an acetylene black EDLC with 1 M NEt₄BF₄ in acetonitrile). - Elemental Analysis Data (contains elemental analysis data). - Gas Sorption Data (.xlsx, .txt - contains results from gas sorption measurements). - XANES Data (contains XANES data from powder samples of Cu₃(HHTP)₂, pristine Cu₃(HHTP)₂ electrodes, cycled Cu₃(HHTP)₂ electrodes from EDLCs, and standard samples). - XRD Data (contains PXRD data).• Oppenheimer Studentship, School of the Physical Sciences, University of Cambridge. • Royal Society University Research Fellowship (UF100278), Royal Society. • UK Materials and Molecular Modelling Hub for computational resources, which is partially funded by EPSRC (EP/P020194/1 and EP/T022213/1). • Royal Society PhD funding, Royal Society. • Winton Programme for the Physics of Sustainability, University of Cambridge. • BP Next Generation Fellowship, Yusuf Hamied Department of Chemistry, University of Cambridge. • UKRI Future Leaders Fellowship (MR/T043024/1), UK Research and Innovation

Insights into the electric double-layer capacitance of two-dimensional electrically conductive metal-organic frameworks.

Two-dimensional electrically conductive metal-organic frameworks (MOFs) have emerged as promising model electrodes for use in electric double-layer capacitors (EDLCs). However, a number of fundamental questions about the behaviour of this class of materials in EDLCs remain unanswered, including the effect of the identity of the metal node and organic linker molecule on capacitive performance, and the limitations of current conductive MOFs in these devices relative to traditional activated carbon electrode materials. Herein, we address both these questions via a detailed study of the capacitive performance of the framework Cu3(HHTP)2 (HHTP = 2,3,6,7,10,11-hexahydroxytriphenylene) with an acetonitrile-based electrolyte, finding a specific capacitance of 110-114 F g-1 at current densities of 0.04-0.05 A g-1 and a modest rate capability. By directly comparing its performance with the previously reported analogue, Ni3(HITP)2 (HITP = 2,3,6,7,10,11-hexaiminotriphenylene), we illustrate that capacitive performance is largely independent of the identity of the metal node and organic linker molecule in these nearly isostructural MOFs. Importantly, this result suggests that EDLC performance in general is uniquely defined by the 3D structure of the electrodes and the electrolyte, a significant finding not demonstrated using traditional electrode materials. Finally, we probe the limitations of Cu3(HHTP)2 in EDLCs, finding a limited stable double-layer voltage window of 1 V and only a modest capacitance retention of 81% over 30 000 cycles, both significantly lower than state-of-the-art porous carbons. These important insights will aid the design of future conductive MOFs with greater EDLC performances.• Oppenheimer Studentship, School of the Physical Sciences, University of Cambridge. • Royal Society University Research Fellowship (UF100278), Royal Society. • UK Materials and Molecular Modelling Hub for computational resources, which is partially funded by EPSRC (EP/P020194/1 and EP/T022213/1). • Royal Society PhD funding, Royal Society. • Winton Programme for the Physics of Sustainability, University of Cambridge. • BP Next Generation Fellowship, Yusuf Hamied Department of Chemistry, University of Cambridge. • UKRI Future Leaders Fellowship (MR/T043024/1), UK Research and Innovation