Multi-parameter study of CO2 electrochemical reduction from concentrated bicarbonate feed

The electrochemical reduction of CO2 (CO2RR) from a concentrated (bi)carbonate solution represents a novel approach of supplying carbon feedstock to a reactor. While this approach achieves comparable performance to gas-feed systems, it substantially reduces the amount of residual CO2 in the output, simplifying the separation of reduction products from unreacted CO2. In this work, the reduction of CO2 to CO from a 2 M KHCO3 solution will be studied by determining the influence of the membrane's polarity, anolyte's pH and temperature on CO2RR in a zero-gap flow cell. These parameters were evaluated by measuring the cell potential, the faradaic efficiency (FECO) and residual CO2 at current densities (J) between 25 and 200 mA cm−2. The results obtained show that bipolar membranes offer a much higher FECO compared to cationic or anionic membranes (∼ 45 % to ∼ 12 % at 200 mA cm−2 at 50 °C) thanks to their ability to dissociate water and produce H+ towards the cathode. However, bipolar membranes exhibit an important drawback in the form of a higher cell potential, and higher residual CO2. The anolyte doesn't affect FECO significantly when the pH stays within an alkaline value. Also, it was confirmed that higher temperatures improve the FECO (especially at higher current densities) while reducing the cell potential. Finally, it was determined that the residual CO2 in the output gas composition stays within 20 %–55 % (at J ≥ 100 mA cm-2), well below the 60–95 % range obtained in systems with gaseous CO2 feed, demonstrating the benefits of working with a bi(carbonate) feedThis work was supported by the Madrid Regional Research Council (CAM) grant n. P2018/EMT-4344 BIOTRES-C

Microstructural description of ion exchange membranes: The effect of PPy-based modification

Properties of ion exchange membranes (IEMs) both cationic and anionic were widely analysed before and after chemical. The modification aims to reduce the crossover phenomena typically observed in RFBs by incorporating polypyrrole (PPy) at the inner of commercial IEMs. In this work, we have explored the insight of membranes by structural and generalized conductivity considerations and its implications in terms of physicochemical characteristics. Transport Structural Parameters (TSP) have been obtained from the electrolyte concentration dependencies (NaCl, in this work). AEMs successfully increased their specific conductivity (between 2.5 and 3.9 times) whereas CEMs slightly decreased (between 1.3 and 2 times). This approach was useful for the description of membrane electro-transport by using the so-called two-phase model which considers an IEM as an heterophase system (particularly, gel and interstitial phase) and their arrangement. AEMs almost doubled increased whereas CEMs doubled decreased their internal microphase arrangement in terms of structural parameter (α). A modification of the established model was applied to the CEMs to better understand their specific behaviour after polymerization. Up to 3.5 times the diffusion coefficient was obtained in AEMs after PPy modification. Finally, based on TSP obtained we propose a microstructural description for the IEMs studied in this workThis work has been funded by the European Union under the HIGREEW project, Affordable High-performance Green Redox Flow batteries (Grant agreement no. 875613) H2020: LC-BAT-4-2019, by the Spanish Ministry of Economy PID 2020-116712RBC21 and Madrid Regional Research Council (CAM) grant. n. P2018/EMT-4344 BIOTRESC

A Cl− hinge for cyclen macrocycles: Ionic Interactions and tweezer-like complexes

The supramolecular networks derived from the complexation of polyazamacrocycles with halide anions constitute fundamental building blocks of a broad range of modern materials. This study provides insights into the conformational framework that supports the binding of protonated cyclen macrocyles (1,4,7,10-Tetraazacyclododecane) by chloride anions through NH δ+ ···Cl - interactions. The isolated complex comprised of two cyclen hosts linked by one Cl - anion is characterized by means of infrared action spectroscopy and ion mobility mass spectrometry, in combination with quantum chemical computations. The Cl - anion is found to act as a hinge that bridges the protonated NH2+ moieties of the two macrocycles leading to a molecular tweezer configuration. Different types of conformations emerge, depending on whether the trimer adopts an open arrangement, with significant freedom for internal rotation of the cyclen moieties, or it locks in a folded conformation with intermolecular H-bonds between the two cyclen backbones. The ion mobility collision cross section supports that folded configurations of the complex are dominant under isolated conditions in the gas phase. The IRMPD spectroscopy experiments suggest that two qualitatively different families of folded conformations coexist at room temperature, featuring either peripheral or inner positions of the anion with respect to the macrocycle cavities, These findings should have implications in the growth of extended networks in the nanoscale and in sensing applicationsThe research leading to this result has been supported by the project CALIPSOplus under the Grant Agreement 730872 from the EU Framework Programme for Research and Innovation HORIZON 2020. This study is part of project P12-FQM-4938 of the research programme of Junta de Andalucia and FEDER

Clean H2 production by lignin-assisted electrolysis in a polymer electrolyte membrane flow reactor

Biomass-derived products, such as lignin, are interesting resources for energetic purposes. Lignin is a natural polymer that, when added to the anode of an alkaline exchange membrane water electrolyser, enhances H2 production rates and efficiencies due to the substitution of the oxygen evolution reaction. Higher efficiencies are reported when different catalytic materials are employed for constructing the lignin anolyte, demonstrating that lower catalytic loadings for the anode improves the H2 production when compared to higher loadings. Furthermore, when a potential of −1.8 V is applied, higher gains are obtained than when −2.3 V is applied. An increase of 200% of H2 flow rates with respect to water electrolysis is reported when commercial lignin is used coupled with Pt-Ru at 0.09 mg cm−2 and E = −1.8 V is applied at the cathode. This article provides deep information about the oxidation process, as well as an optimisation of the method of the lignin electro-oxidation in a flow-reactor as a pre-step for an industrial implementationThis work was supported by the Madrid Regional Research Council (CAM) and ERDF (European Regional Development Fund), grant no. P2018/EMT-4344 BIOTRES-CM. We thank the Spanish Ministry of Economy, PID 2020-116712RBC21 funded by MCIN/AEI/10.13039/501100011033 is acknowledge

Outstanding inhibition of H2O2 generation in doubly doped graphene: The synergy of two heteroatoms opens a new chemical path

Dual sulfur-nitrogen (SN) doped graphene surfaces have been revealed as a powerful active material in fuel cell applications. The experimental results presented in this work show a clear preference of the material doped with SN towards a 4-electron mechanism, almost completely inhibiting the formation of H2O2. However, materials doped only with nitrogen (N) or sulfur (S) favor the 2-electron mechanism, and therefore, the production of H2O2. A reasonable theoretical explanation is proposed to justify the inhibition of the H2O2 reaction with the use of SN doped graphenes in accordance with the experimental results. The interactions and charge transfer between N and S are the origin of an alternative dissociative step that inhibits the generation of H2O2, which is energetically favored, according to Density Functional Theory (DFT) calculations. These two dopant atoms generate a frustrated Lewis pair (FLP), resulting in an enhancement of the catalytic activity of the graphene. Atomic Dipole Corrected Hirshfeld charges (ADCH model) and Non-Covalent Interactions (NCI) are employed to identify the most active sites and support the explanation of the dissociative pathway which inhibits H2O2 formationP2018/EMT-4344 BIOTRES-CM, PID2020-116712RBC21, PID2020-117586RB-I00, PID2022-138470NB-I00, PID2019-110091 GB-I0

DFT calculation, a practical tool to predict the electrochemical behaviour of organic electrolytes in aqueous redox flow batteries

Herein, a computational predictive tool for redox flow batteries based on NBO and ADCH charge distribution studies is presented and supported by experimental evidence. Using highly water soluble (>2 M) non-planar 2,2′ - bipyridinium salts as a case of study, this work presents a DFT protocol that successfully predicts the stability and forecasts their potential application as active materials for Aqueous Organic Redox Flow Batteries (AORFB). An initial theoretical-experimental characterization of selected bipyridines served to determine the effect of the ring size, geometry, and electron density on the physico-chemical properties of the materials. Nonetheless, the NBO and ADCH charge analyses were essential tools to understand the stability of the reduced species in terms of electronic delocalization and the importance of the molecular design on the stability of electrolyte for AORFB. Based on these results, the cell performance of seven-membered 2,2′ -bypiridinium salt, (2), and m-Me substituted homologous, (4), were compared. The significantly lower capacity decay rendered by compound 4 based electrolyte, (0.35%/cycle) compared with compound 2 based electrolyte, (0.71%/cycle) was in good agreement with the predicted stability. The aim of this work is to highlight the powerful synergy between DFT calculations and organic chemistry in predicting the behaviour of different negolytesThis work has been funded by the European Union under the HIGREEW project, Affordable High-performance Green Redox Flow batteries (Grant agreement no. 875613). H2020: LC-BAT-4-2019. A.C. Lopes acknowledges the Ramon y Cajal (RYC2021-032277-I) research fellowship, the financial support from Ministerio de Ciencia e Innovacion ´ / AEI /10.13039/501100011033 and from European Union NextGenerationEU/PRTR. We also thank the CCC-UAM (Graforr project) for allocation of computer tim

A Spectroscopic study of colchicine in the solid state and in solution by multinuclear magnetic resonance and vibrational circular dichroism

Although almost 200-years-old, several unknown aspects remain to be explored of colchicine, the unique available drug for acute flares of gout. In this article, we report density-functional theory (DFT) studies of geometry, energy, and NMR; 1H-, 13C-, and 15N-NMR chemical shifts and some spin-spin coupling constants, including the complete analysis of the saturated part (ring B); the assignment of both enantiomers by NMR using a chiral solvating agent; solid-state NMR experiments of the different forms of natural and racemic colchicine, and IR and vibrational circular dichroism (VCD) studies of these same forms. Copyright © 2014 Verlag Helvetica Chimica Acta AG, Zürich.Peer Reviewe

Characterization of lignin and lignin-derivatives from biomass. Application as expander of lead-acid battery

Expanders, as lignosulfonates, are crucial for a good performance of Pb/acid batteries. In the process of discharge, the Pb and the PbO2 go to PbSO4. The formed PbSO4 is adsorbed on the surface of the Pb electrode and dramatically reduces the lifetime of the battery by the formation of big PbSO4 crystals. In order to prevent that, the addition of expanders in the negative electrode is an economic solution to prevent the formation of big crystals. In this investigation, we propose the synthesis of several lignosulfonates obtained from lignin of many biomass origins. We have derivatized nine samples of lignin via microwave-assisted sulfonation, then we have characterized how efficient is the chosen synthesis method. The lignosulfonates obtained have been characterized by infrared spectroscopy (IR), proton nuclear magnetic resonance (1HNMR), two-dimensional correlated spectroscopy (COSY), and elemental analysis to acquire some relevant information about their structure in terms of functional groups. In this way, three commercial lignosulfonates, Vanisperse A, Indulin AT, and Oakwood, have been selected as references for our comparisons. Moreover, we have checked their electrochemical properties, using electrochemical techniques to compare their behavior with respect to the commercial lignosulfonates. Finally, we have selected one of them and we have tested its performance as an expander in a Pb/acid battery. That result is a very promising first approach, and we can conclude that lignosulfonates derivatives are a good and low-cost choice to improve the lifetime of Pb/acid batteries. In particular, it is shown that the incorporation of LignosB improves the cell formation as well as the first capacity (36.30% more) and the charge acceptance (63.16% more), being these relevant parameters in the performance of Pb/acid batterie

Treatment with tocilizumab or corticosteroids for COVID-19 patients with hyperinflammatory state: a multicentre cohort study (SAM-COVID-19)

Objectives: The objective of this study was to estimate the association between tocilizumab or corticosteroids and the risk of intubation or death in patients with coronavirus disease 19 (COVID-19) with a hyperinflammatory state according to clinical and laboratory parameters. Methods: A cohort study was performed in 60 Spanish hospitals including 778 patients with COVID-19 and clinical and laboratory data indicative of a hyperinflammatory state. Treatment was mainly with tocilizumab, an intermediate-high dose of corticosteroids (IHDC), a pulse dose of corticosteroids (PDC), combination therapy, or no treatment. Primary outcome was intubation or death; follow-up was 21 days. Propensity score-adjusted estimations using Cox regression (logistic regression if needed) were calculated. Propensity scores were used as confounders, matching variables and for the inverse probability of treatment weights (IPTWs). Results: In all, 88, 117, 78 and 151 patients treated with tocilizumab, IHDC, PDC, and combination therapy, respectively, were compared with 344 untreated patients. The primary endpoint occurred in 10 (11.4%), 27 (23.1%), 12 (15.4%), 40 (25.6%) and 69 (21.1%), respectively. The IPTW-based hazard ratios (odds ratio for combination therapy) for the primary endpoint were 0.32 (95%CI 0.22-0.47; p < 0.001) for tocilizumab, 0.82 (0.71-1.30; p 0.82) for IHDC, 0.61 (0.43-0.86; p 0.006) for PDC, and 1.17 (0.86-1.58; p 0.30) for combination therapy. Other applications of the propensity score provided similar results, but were not significant for PDC. Tocilizumab was also associated with lower hazard of death alone in IPTW analysis (0.07; 0.02-0.17; p < 0.001). Conclusions: Tocilizumab might be useful in COVID-19 patients with a hyperinflammatory state and should be prioritized for randomized trials in this situatio