A Review of Electrolyte Additives in Vanadium Redox Flow Batteries.

Vanadium redox flow batteries (VRFBs) are promising candidates for large-scale energy storage, and the electrolyte plays a critical role in chemical-electrical energy conversion. However, the operating temperature of VRFBs is limited to 10-40 °C because of the stability of the electrolyte. To overcome this, various chemical species are added, but the progress and mechanism have not been summarized and discussed yet. This review summarizes research progress on electrolyte additives that are used for different purposes or systems in the operation of VRFBs, including stabilizing agents (SAs) and electrochemical mass transfer enhancers (EMTEs). Additives in vanadium electrolytes that exhibit microscopic stabilizing mechanisms and electrochemical enhancing mechanisms, including complexation, electrostatic repulsion, growth inhibition, and modifying electrodes, are also discussed, including inorganic, organic, and complex. In the end, the prospects and challenges associated with the side effects of additives in VRFBs are presented, aiming to provide a theoretical and comprehensive reference for researchers to design a higher-performance electrolyte for VRFBs.

Gut microbiome interacts with pregnancy hormone metabolites in gestational diabetes mellitus.

Introduction: Change in the composition of intestinal microbiota is associated with metabolic disorders such as gestational diabetes mellitus (GDM). Methods: To understand how the microbiota impacts the development of gestational diabetes mellitus, we profiled the intestinal microbiome of 54 pregnant women, including 27 GDM subjects, by employing 16S rRNA gene sequencing. Additionally, we conducted targeted metabolomics assays to validate the identified pathways with overrepresented metabolites. Results: We evaluated the patterns of changing abundances of operational taxonomic units (OTU) between GDM and the healthy counterparts over three timepoints. Based on the significant OTUs, we inferred 132 significantly altered metabolic pathways in GDM. And identified two overrepresented metabolites of pregnancy hormone, butyrate and mevalonate, as potential intermediary metabolites of intestinal microbiota in GDM. Finally, we validated the impacts of the intestinal microbiota on GDM by demonstrating consistent changes of the serum levels of progesterone, estradiol, butyrate, and mevalonate in an independent cohort. Discussion: Our findings confirm that alterations in the microbiota play a role in the development of GDM by impacting the metabolism of pregnancy hormones. This provides a novel perspective on the pathogenesis of GDM and introduces potential biomarkers that can be used for early diagnosis and prevention of the disease.

Analysis of anti-M antibody status and blood transfusion strategy in Hunan, China.

Background: By analyzing the detection rate of anti-M antibody in patients with the MNS blood group system in the Hunan area, we aimed to explore its clinical significance and blood transfusion strategy. Methods: We retrospectively analyzed the clinical data of patients who had been confirmed to contain anti-M antibodies through serological methods such as the saline tube method and cassette anti-human globulin method. Results: Irregular antibody screening tests had been applied to 94,452 patients, from which 652 results were positive. Among those positive patients, 93 cases were positive for anti-M antibodies, accounting for 14.26% of the positive rate of irregular antibodies; 11 cases had a blood transfusion history, accounting for 11.8%; 59 cases had a pregnancy history, accounting for 63.4%; and 2 cases had a transplant history, accounting for 2.2%. The patients with anti-M antibodies included 23 pregnant woman, accounting for 24.7%, and 19 tumor patients, accounting for 20.4%. A total of 66 cases were immunoglobulin M (IgM) + immunoglobulin G (IgG) class, accounting for 71.0%, 26 cases were IgM class, accounting for 28.0%, and 1 case was IgG class, accounting for 1.0%. Conclusions: The detection rates of anti-M antibody in the Hunan area and unexpected antibodies in literature reports are mainly related to a pregnancy history, and the type of antibody is predominantly IgM + IgG class. The clinical significance of anti-M antibody cannot be ignored, and three media should be used for cross-matching of blood wherever possible to ensure the safety of blood transfusion.

Oxidative leaching of V-Cr-bearing reducing slag via a Cr(III) induced Fenton-like reaction in concentrated alkaline solutions.

V-Cr-bearing reducing slag (VCRS) is considered a hazardous waste that can create ecosystem disasters if handled improperly. It consists of a considerable amount of heavy metals, such as vanadium (V) and chromium (Cr). In this study, we propose a novel process featuring a VCRS self-induced Cr(III)-Fenton-like reaction to efficiently recover V and Cr from hazardous VCRS. The generation of hydroxyl radicals (·OH) and determination of their effect on V and Cr oxidation were examined via electron spin resonance detection, free radical quenching, and terephthalic acid fluorescence probe methods. The V and Cr oxidative leaching processes were directly controlled by the amount of added H2O2 and generated·OH from the Cr(III)-Fenton-like reaction, which in turn was dependent on the amount of dissolved Cr(OH)4-. In a single oxidative leaching process, the leaching efficiencies of V and Cr reached 97.5 ± 0.6 % and 85.2 ± 0.8 %, respectively, and reached 99.4 ± 0.5 % and 94.6 ± 0.9 %, respectively, from circular leaching owing to a continuous supply of dissolved Cr(OH)4- from fresh VCRS. This study identifies a novel approach to discovering deep oxidation of the VCRS while minimizing environmental contamination via a waste control strategy and can be considered an attractive alternative approach for the green treatment of VCRS.

Role of Noncovalent Interactions on the Electrocatalytic Oxidation of Ethanol in Alkali Metal Hydroxide Solutions.

Ethanol is considered to be one of the most promising fuels for fuel cells. However, ethanol fuel cells have a sluggish Faraday efficiency due to complex interactions between the electrolyte, electrode, and ethanol. Recent studies have further suggested that noncovalent interactions originated from the hydrated alkali metal cations and the adsorbed OHad at the Pt electrode surface also played an important role in the electron transfer. In this regard, the noncovalent interactions in different alkali metal hydroxide (AMH) solutions have been systematically investigated in this study, and it was observed that the noncovalent interactions could result in the occupation of the Pt electrode surface active sites and sluggish migration of ethanol molecules in the electrical double layer, significantly affecting the electro-oxidation efficiency. Further, it was concluded that the electro-oxidation efficiency in different AMH solutions followed the order of K+ > Na+ > Rb+ > Cs+ > Li+ due to the noncovalent interactions.

Anaerobic biodegradation of four sulfanilamide antibiotics: Kinetics, pathways and microbiological studies.

Large amounts of sulfanilamide antibiotics (SAs) have been excreted into the manure. In this study, the anaerobic biodegradation of four kinds of SAs including sulfaquinoxaline (SQX), sulfamethoxazole (SMX), sulfamethoxine (SMD) and sulfathiazole (STZ) was investigated. The degradation rates of SQX and STZ decreased with the increase of the concentrations of other organics, but those of SMX and SMD were less affected. The average degradation rates of SAs were in the order of SMX >SMD ≈QX >STZ, with the best degradation rate constants of 0.30125, 0.14752, 0.16696, and 0.06577 /d, respectively. STZ had the greatest effect on the population richness of microbes, whereas SQX had the largest impact on the population diversity. The degradation rates of SAs were positively correlated with the abundances of Proteobacteria and Bacteroidetes, and negatively correlated with the abundance of Firmicutes. The common degradation pathways of SAs were S-N cleavage and substitution. The specific functional groups of SQX, SMX and SMD, including quinoxaline, isoxazole and pyrimidine rings, could be opened, but the thiazole ring of STZ was difficult to be decomposed. After the rings of the specific functional groups were opened, they would be further substituted or decomposed to be products with small molecules.

Recovering valuable metals from spent hydrodesulfurization catalyst via blank roasting and alkaline leaching.

Spent hydrodesulfurization (HDS) catalysts, containing considerable amount of pollutants and metals including vanadium (V), molybdenum (Mo), aluminum (Al), and nickel (Ni), are considered as hazardous wastes which will result in not only ecosystem damage but also squandering resource. Herein, a process featuring blank roasting-alkaline leaching is proposed to recover spent HDS catalyst. During roasting, low-valence compounds convert to high-valence oxides which can be leached out by NaOH solution. Afterwards, leaching solution is subjected to crystallization to separate metals. The results show that for samples roasted at 650 °C, 97% V, 96% Mo, and 88% Al are leached out at optimal condition; for samples roasted at 1000 °C, selective leaching of 91% V and 96% Mo respectively, are realized, with negligible Al being dissolved. NiO is insoluble in strong alkali leaving in residue. The advantages of this process are that first, the leaching of V, Mo, and Al can be manipulated by controlling roasting conditions, providing flexible process design. Second, leaching solution can be fully recycled. Finally, mild leaching condition and clean separation of V, Mo, and Al is achieved, proving fundamental information for peer researches to facilitate their future research on the development of more efficient and cleaner technologies.

Potassium Hydroxide Concentration-Dependent Water Structure on the Quartz Surface Studied by Combining Sum-Frequency Generation (SFG) Spectroscopy and Molecular Simulations.

Vibrational sum-frequency generation (SFG) spectroscopy and molecular simulations were used to investigate the molecular structures at the quartz surface, and the influence of bulk potassium hydroxide concentration was systematically examined. It was found that when the potassium hydroxide concentration was less than 10-2 M, the structure of water molecules at the quartz surface was dependent on the quartz surface potential as evidenced by the increase of SFG signal as a function of the alkaline concentration. However, when the alkaline concentration was more than 10-2 M, a monotonic decrease of interfacial water SFG spectra intensity was observed, which has been proposed to be due to the decreased number of interfacial water molecules and proton disordering caused by the screening effect originated from the adsorption of cations. Furthermore, besides the typical hydrogen-bonded interfacial water peaks (3200 and 3400 cm-1), the quartz/H2O interface showed an additional red-shifted peak centered at ∼2930 cm-1. The results of SFG spectra and chemistry calculations confirmed that the red-shifted vibrational peak was due to the O-H stretch vibration of water molecules strongly hydrogen bonded with the OH- adsorbed at the surface.

High-Rate and Long-Term Cycle Stability of Li-S Batteries Enabled by Li2S/TiO2-Impregnated Hollow Carbon Nanofiber Cathodes.

The high theoretical energy density of lithium-sulfur (Li-S) batteries makes them an alternative battery technology to lithium ion batteries. However, Li-S batteries suffer from low sulfur loading, poor charge transport, and dissolution of lithium polysulfide. In our study, we use the lithiated S, Li2S, as the cathode material, coupled with electrospun TiO2-impregnated hollow carbon nanofibers (TiO2-HCFs), which serve as the conductive agent and protective barrier for Li2S in Li-S batteries. TiO2-HCFs provide much improved electron/ionic conductivity and serve as a physical barrier, which prevents the dissolution of lithium polysulfides. The Li2S/TiO2-HCF composite delivers a discharge capacity of 851 mA h gLi2S-1 at 0.1C and the bilayer TiO2-HCFs/Li2S/TiO2-HCF composite delivers a high specific capacity of 400 mA h gLi2S-1 at 5C.

Adsorption behaviors and vibrational spectra of hydrogen peroxide molecules at quartz/water interfaces.

The effect of H2O2 concentration on the change of H-bonds at a water/quartz interface was systematically examined by surface-specific sum-frequency generation (SFG) spectroscopy. Molecular dynamics (MD) simulation was further utilized to interpret the specific molecular dynamics as well as the configuration and evolution of water and H2O2 molecules at the interface. The results from this study demonstrated the important role of surface H-bonds on determination of the stability of adsorbed H2O2 at solvated, silica, xerogel surfaces. It was revealed that prior to reaching the surface saturation with H2O2 molecules (less than 20% in bulk solution), multiple H-bonds were formed with silanols at relatively short interactive distances. These H-bonds proved to be strong enough to enable the overall stability of adsorbed H2O2. However, once saturated, the H2O2 molecules would be adsorbed at longer distances away from the surface, and could easily migrate to the bulk solution; therefore, in this case, the bonds failed to support stable H2O2 adsorption. These new findings explained the detailed molecular mechanism of the relationship between H2O2 concentration and H2O2 stability in H2O2-silica xerogels. This solves the current challenge of effective H2O2 storage, and provides fundamental insight for predicting the adsorption behavior of H2O2 at the silica surface.