Complexing additives to reduce the immiscible phase formed in the hybrid ZnBr2 flow battery

The zinc-bromine redox flow battery (RFB) is one of a very few commercially viable RFB energy storage system capable of integration with intermittent renewable energy sources to deliver improved energy management. However, due to the volatility of the electrogenerated bromine and potential for its crossover from positive to negative electrolytes, this system requires the use of quaternary ammonium complexes (N-methyl-N-ethylpyrrolidinium, (MEP)) to capture this bromine. This produces an immiscible phase with the Br2 which requires a complex network of pipes, pumps and automated controls to ensure access to the electroactive material during discharge. In this work, the use of novel quaternary ammonium complexes to capture the electrogenerated bromine but to keep it in the aqueous phase is examined. Three compounds, 1-(carboxymethyl) pyridine-1-ium, 1-(2-carboxymethyl)-1-methylmorpholin-1-ium and 1-(2-carboxymethyl)-1-methylpyrrolidin-1-ium, were found to successfully reduce the volume of the immiscible phase formed on complexing with the polybromide (Brx-) whilst displaying similar enthalpy of vaporisation values as that of MEP. Electrochemical analysis also revealed that these compounds did not impact on the electrode kinetics of the Br-/Brx- reaction indicating that the resulting surface film formed with these compounds behaved as a chemically modified electrode, in contrast to the surface film formed with MEP

Scalable slot-die coated flexible supercapacitors from upcycled PET face shields

\ua9 2024 The Royal Society of Chemistry.Upcycling Covid19 plastic waste into valuable carbonaceous materials for energy storage applications is a sustainable and green approach to minimize the burden of waste plastic on the environment. Herein, we developed a facile single step activation technique for producing activated carbon consisting of spherical flower like carbon nanosheets and amorphous porous flakes from used PET [poly(ethylene terephthalate)] face shields for supercapacitor applications. The as-obtained activated carbon exhibited a high specific surface area of 1571 m2 g−1 and pore volume of 1.64 cm3 g−1. The specific capacitance of these carbon nanostructure-coated stainless steel electrodes reached 228.2 F g−1 at 1 A g−1 current density with excellent charge transport features and good rate capability in 1 M Na2SO4 aqueous electrolyte. We explored the slot-die coating technique for large-area coatings of flexible high-performance activated carbon electrodes with special emphasis on optimizing binder concentration. Significant improvement in electrochemical performance was achieved for the electrodes with 15 wt% Nafion concentration. The flexible supercapacitors fabricated using these electrodes showed high energy and power density of 21.8 W h kg−1 and 20 600 W kg−1 respectively, and retained 96.2% of the initial capacitance after 10 000 cycles at 2 A g−1 current density. The present study provides a promising sustainable approach for upcycling PET plastic waste for large area printable supercapacitors

The core minimum dataset for measuring pain outcomes in pain services across Scotland. Developing and testing a brief multi-dimensional questionnaire

BACKGROUND: There is currently no agreed minimum dataset to inform specialist chronic pain service provision. We aimed to develop a Core Minimum Dataset (CMD) for pain services in Scotland and perform preliminary analysis to evaluate its psychometric properties in adults with chronic pain. METHODS: The questionnaire was developed following a review of existing relevant data collection instruments and national consultation. The CMD questionnaire was completed alongside a routine pre-clinic questionnaire by patients attending two pain services over 3 months. Concurrent validity was tested by comparing scores between the CMD and pre-existing questionnaires. Reliability was assessed by test-retest and discriminative validity via receiver operating characteristic (ROC) curves. RESULTS: The final CMD questionnaire consisted of five questions on four domains: pain severity (Chronic Pain Grade [CPG] Q1); pain interference (CPG Q5); emotional impact (Patient Health Questionnaire-2 [PHQ-2], two questions); and quality of life (Short Form Health Survey-36 [SF-36] Q1). 530 patients completed the questionnaire. Strong correlation was found with the Hospital Anxiety and Depression Scale (r(s) = 0.753, p < 0.001). Moderate correlations were found with the Brief Pain Inventory for pain interference (r(s) = 0.585, p < 0.001) and pain severity (r(s) = 0.644, p < 0.001). Moderate to good reliability was demonstrated (Intra-class Correlation Coefficient = 0.572–0.845). All items indicated good discrimination for relevant health states. CONCLUSIONS: The findings represent initial steps towards developing an accurate questionnaire that is feasible for assessing chronic pain in adults attending specialist pain clinics and measuring service improvements in Scotland. Further validation testing, in clinical settings, is now required

Changes in hydrogen storage properties of carbon nano-horns submitted to thermal oxidation

The effect of thermal oxidation on the hydrogen storage properties of carbon nano-horns was investigated by gravimetric and electrochemical methods. The pristine nano-horn sample was oxidised at 673 K in air for different periods (15, 30 and 60 min) and the resulting materials were characterised. The N2 adsorption experiments reveal a marked increase in the surface area, from 267 m2 g-1, for the pristine sample, up to 1360 m2 g-1 for the sample oxidised for the 60 min period, and a reduction in the average pore diameter. The gravimetric investigation, conducted at low temperature (77 K) showed an increase in the hydrogen storage, from 0.75 wt% for the pristine sample up to 2.60 wt% for the oxidised material. Reproducible and stable hydrogen storage was found for all the samples examined apart from the sample oxidised for 60 min. For the latter, a decrease in the amount of hydrogen stored between the first and second cycles was found. Electrochemical loading of hydrogen in the samples was performed at room temperature (298 K) in alkaline solution by the galvanostatic charge/ discharge technique. The results obtained here however show a much lower hydrogen storage level by the samples as compared to the gas storage method, with a maximum value of 0.124 wt% H2 and with very little dependence on the thermal oxidation treatment

Modelling the impact of geometric parameters on the redox potential of blue copper proteins

The synthesis and structure of a homologous series of cationic N2S2 copper(I) Schiff base complexes constructed using o-tert-butylthiobenzaldehyde and a series of terminal diamines (ethane, propane, butane) are reported. The complexes differ only in the length of the methylene chain between the imine groups. This simple modification forces the copper centre to shift geometry from a planar (1,2-diaminoethane) to a more distorted tetrahedral motif (1,4-diaminobutane). The redox potentials of the three cations were measured using cyclic voltammetry in donor (acetonitrile) and non-donor solvents (dichloromethane). The S-Cu-N angles for each complex are correlated against the respective redox potential allowing an analysis of the geometric impact on the redox potential in soft copper centres. The redox potential is observed to increase as the metal centre moves from a planar towards a tetrahedral motif. Comparing this data with the reported structures of the blue copper proteins (rusticyanin and plastocyanin) allows an assessment of the contribution of the geometry of the metal binding site to the operating potential of these proteins to be made

The effect of donor groups and geometry on the redox potential of copper Schiff base complexes

We report a study which correlates the metrical parameters of the unsubstituted tetradentate copper Schiff base complexes containing N2O2, N2N2 and N2S2 donors with their respective redox potentials. To achieve this aim we were required to structurally characterise many of the seminal species including, [CuAmbpr-H-2] [CuH(4)Amben][ClO4](2), [CuH(4)Ambpr][ClO4](2), [CuH(4)Ambbu][ClO4](2), CuH(4)Salpr and [Cu(SSalen)(2)][ClO4](2) which were absent from the crystallographic catalogue. The oxidative dehydrogenation of CuH(4)Salen is revisited through the isolation and structural characterisation of (N-salicyl-N'-salicylidene-1,2-ethylenediamine)copper(II) (CuH(3)Salen). The redox potentials of the three series of compounds are measured, clearly identifying the operating ranges of each donor set. The modulating effect of coordination geometry on redox potential is evident in the series of N2O2 complexes. This study forms the basis of the rational synthesis of tuneable copper redox sensors by demonstrating the regions in which the various donor sets operate. (c) 2006 Elsevier B.V. All rights reserved