Oxygen Scavenging Research Articles

Effect of Reactive Oxygen Scavenger N,N'-Dimethylthiourea (DMTU) on Seed Germination and Radicle Elongation of Maize.

Reactive oxygen species (ROS) are an important part of adaptation to biotic and abiotic stresses and regulate seed germination through positive or negative signaling. Seed adaptation to abiotic stress may be mediated by hydrogen peroxide (H2O2). The effects of the ROS scavenger N,N'-dimethylthiourea (DMTU) on maize seed germination through endogenous H2O2 regulation is unclear. In this study, we investigated the effects of different doses of DMTU on seed endogenous H2O2 and radicle development parameters using two maize varieties (ZD958 and DMY1). The inhibitory effect of DMTU on the germination rate and radicle growth was dose-dependent. The inhibitory effect of DMTU on radicle growth ceased after transferring maize seeds from DMTU to a water medium. Histochemical analyses showed that DMTU eliminated stable H2O2 accumulation in the radicle sheaths and radicles. The activity of antioxidant enzyme and the expression of antioxidant enzyme-related genes (ZmAPX2 and ZmCAT2) were reduced in maize seeds cultured with DMTU compared with normal culture conditions (0 mmol·dm-3 DMTU). We suggest the use of 200 mmol·dm-3 DMTU as an H2O2 scavenger to study the ROS equilibrium mechanisms during the germination of maize seeds, assisting in the future with the efficient development of plant growth regulators to enhance the seed germination performance of test maize varieties under abiotic stress.

Mechanical property and microstructure of in-situ TiB/Ti64 composites via adding oxygen scavenger CaB6

Powder metallurgy in-situ TiB/Ti6Al4V composites with good mechanical properties are fabricated by vacuum sintering using high-oxygen HDH Ti6Al4V and CaB6 powders. CaB6 can not only be used as a boron source, but also synthesize Ca-Ti-O ternary compounds with solid solution oxygen in titanium matrix. Therefore, it has a purification effect on oxygen scavenging, and the relative density of TiB/Ti6Al4V composites can exceed 99%. The interface between titanium matrix and TiB is semi-coherent. Good interfacial adhesion, high density, and reduced oxygen content make the composite material exhibit higher ductility. Although the equivalent oxygen content for Ti6Al4V-0.1CaB6 composite material is about 0.57 wt%, the elongation still reaches 9.5%, which is 57.4% higher than that of CaB6-free sample. Besides, the ultimate tensile strength reaches 1015.6 MPa, and the yield strength is 932.0 MPa.

Genetic dissection of cold tolerance at the budding stage of rice in an indica-japonica recombination inbred line population

Rice is highly cold-sensitive, and thus, the promotion of cold resistance in buds is essential. In this study, we conducted a mapping analysis to identify quantitative trait loci (QTLs) associated with cold tolerance in buds. The analysis was performed using a recombinant inbred line (RIL) population consisting of 192 lines derived from the cold-tolerant strain 02428 and the cold-sensitive strain YZX. Seven additive loci on chromosomes 1, 4, 5, and 6 were identified, of which loci 3 and 7 were found in two crop seasons, indicating stability. Three epistatic interactions, one present over two seasons, were found. Loci 3 and 7 pyramided with two main-effect QTLs observed to control the rate of low-temperature germination in our previous study. Two materials with good cold resistance at the germination and bud stages were obtained, namely, G93 and G146. Transcriptome sequencing analysis of the two parent buds after cold treatment found that genes expressed differentially between the two parents were related to photosynthesis, energy metabolism, and reactive oxygen scavenging. Five candidate genes, namely, Os01g0385400, Os01g0388000, Os06g0287700, Os06g0289200, and Os06g0291100, were selected in the two stable intervals based on gene expression profiles and annotations. These genetic loci exhibit strong potential as targets for breeding cold tolerance in buds and require additional investigation. In conclusion, this work provides valuable genetic resources that can be utilized to improve the cold tolerance of rice.

Evaluation of Oxygen Absorbers Using Food Simulants and Inductively Coupled Mass Spectrometry.

In this study, we developed and validated an analytical method to evaluate the heavy metal elution from an active packaging material's oxygen absorber to a food simulant. Using water, 4% acetic acid, n-heptane, 20% ethanol, and 50% ethanol as food simulants, we quantified cobalt, copper, platinum, and iron with inductively coupled plasma-mass spectrometry. The method was thoroughly validated for linearity, accuracy, precision, LOD, and LOQ through inter-day and intra-day analysis repetitions. R2 values ranged from 0.9986 to 1.0000, indicating excellent linearity. The LOD values ranged from 0.00002 to 0.2190 mg/kg, and the LOQ values ranged from 0.00007 to 0.6636 mg/kg. The method's accuracy was 95.14% to 101.98%, with the precision ranging from 0.58% to 10.37%. Our results confirmed the method's compliance with CODEX standards. Monitoring the oxygen absorber revealed undissolved platinum, cobalt levels from 0.10 to 19.29 μg/kg, copper levels from 0.30 to 976.14 μg/kg, and iron levels from 0.06 to 53.08 mg/kg. This study established a robust analytical approach for evaluating the heavy metal elution from oxygen absorbers, ensuring safety in the food industry.

Effects of Acetic Acid on the Initiation of Pitting Corrosion and Stress Corrosion Cracking on Low-Alloy Steel in pH Buffer Solutions

Applying organic chemicals as an oxygen scavenger or a corrosion inhibitor to the water treatment of steam-water circuits of power plants possibly results in the generation of organic acids, such as acetic acid. This necessitates assessing the effects of the generated organic acids on the corrosion of the steam-water circuits prior to applying the organic chemicals. In this research, the effects of acetic acid on pitting corrosion and stress corrosion cracking (SCC) on low-pressure turbine materials of low-alloy steel were examined by electrochemical measurements and U-bend tests. Buffer solutions of various pHs from 4.5 to 10 were used as test solutions to investigate the effects of acidification by acetic acid on corrosion. Electrochemical measurements indicated that the steel was passivated at pHs above 8 and was the most susceptible to pitting corrosion at pH 8. In the U-bend test, SCC was initiated readily at a pH of around 8. Because SCC occurred at sites of pitting corrosion, pitting corrosion was suggested to be a precursor of SCC. Acetate ions did not trigger pitting corrosion or SCC on the steel. Rather, the addition of acetate ions to a Cl−-containing solution mitigated the initiation of pitting corrosion, resulting in the inhibition of SCC initiation.

Application of oxygen scavengers in gel electromembrane extraction: A green methodology for simultaneous determination of nitrate and nitrite in sausage samples.

The generation of oxygen from electrolysis in gel electromembrane extraction (G-EME) causes a negative error when applied to the analysis of easily oxidized species such as nitrite. Nitrite in G-EME is oxidized by oxygen to nitrate, leading to the negative error and the impossibility of simultaneous analysis. In this work, the application of oxygen scavengers to the acceptor phase of the G-EME system was attempted to minimize the oxidation effect. Several oxygen scavengers were selected and examined according to their compatibility with ion chromatography. The mixture of sulfite and bisulfite (14mg L-1) showed the highest efficiency in preventing the oxidation of nitrite to nitrate. Under the optimized conditions, a good linear range was obtained (10-200μg L-1; R2>0.998) with a detection limit of 8µg L-1 for both nitrite and nitrate. This method was applied to the simultaneous determination of nitrite and nitrate in sausage samples.

RsCDF3, a member of Cycling Dof Factors, positively regulates cold tolerance via auto-regulation and repressing two RsRbohs transcription in radish (Raphanus sativus L.)

Radish is one of the most economical root vegetable crops worldwide. Cold stress dramatically impedes radish taproot formation and development as well as reduces its yield and quality. Although the Cycling Dof Factors (CDFs) play crucial roles in plant growth, development and abiotic stress responses, how CDF TFs mediate the regulatory network of cold stress response remains largely unexplored in radish. Herein, a total of nine RsCDF genes were identified from the radish genome. Among them, the RsCDF3 exhibited obviously up-regulated expression under cold stress, especially at 12 h and 24 h. RsCDF3 was localized to the nucleus and displayed dramatic cold-induced promoter activity in tobacco leaves. Moreover, overexpression of RsCDF3 significantly enhanced cold tolerance of radish plants, whereas its knock-down plants exhibited the opposite phenotype. Interestingly, both in vitro and in vivo assays indicated that the RsCDF3 repressed the transcription of RsRbohA and RsRbohC via directly binding to their promoters, which contributed to maintaining the cellular homeostasis of reactive oxygen species (ROS) production and scavenging in radish. In addition, the RsCDF3 bound to its own promoter to mediate its transcription, thereby forming an autoregulatory feedback loop to cooperatively trigger RsRbohs-dependent cold tolerance. Together, we revealed a novel RsCDF3-RsRbohs module to promote the cold tolerance in radish plants. These findings would facilitate unveiling the molecular mechanism governing RsCDF3-mediated cold stress response in radish.

Designing an Oxygen Scavenger Multilayer System Including Volatile Organic Compound (VOC) Adsorbents for Potential Use in Food Packaging.

Oxygen scavengers are valuable active packaging systems because several types of food deterioration processes are initiated by oxygen. Although the incorporation of oxygen scavenger agents into the polymeric matrices has been the trend in recent years, the release of volatile organic compounds (VOC) as a result of the reaction between oxygen and oxygen scavenger substances is an issue to take into account. This is the case of an oxygen scavenger based on a trans-polyoctenamer rubber (TOR). In this work, the design of an oxygen scavenger multilayer system was carried out considering the selection of appropriate adsorbents of VOCs to the proposed layer structure. Firstly, the retention of some representative organic compounds by several adsorbent substances, such as zeolites, silicas, cyclodextrins and polymers, was studied in order to select those with the best performances. A hydrophilic silica and an odor-adsorbing agent based on zinc ricinoleate were the selected adsorbing agents. The principal VOCs released from TOR-containing films were carefully identified, and their retention first by the pure adsorbents, and then by polyethylene incorporated with the selected compounds was quantified. Detected concentrations decreased by 10- to 100-fold, depending on the VOC.

Antioxidative capacity evaluation of imine compounds as metal ions chelators and free radical scavengers in biodiesel

Factors affecting the oxidation stability of commercially available biodiesel were primarily investigated using the acid value (AV), peroxide value (PV), 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay, and thermogravimetric (TG) analysis in the presence of imine antioxidants. In this study, the imine compounds N,N′-bis-(4-octadecanate)-salicyl ethylenediamine (stearic dhben) and N,N′-bis-(4-hexadecanate)-salicyl ethylenediamine (palmitic dhben) were synthesized to evaluate their abilities as metal chelators and oxygen scavengers. The AV analysis showed a slight difference between the samples with and without copper. The PV tests demonstrated that both imines were efficient free radical scavengers and copper ion chelators at both room temperature and 50 °C, outperforming the commercial antioxidants butylhydroxytoluene (BHT) and tert-butylhydroquinone (TBHQ). The Derivative Thermogravimetry (DTG) curves indicated that both imines were more effective compared to commercial antioxidants. In the DPPH assay, it was observed that the palmitic dhben imine exhibited the best performance, with an half maximal inhibitory concentration (IC50) of 12.4·10−5 mol L−1. Therefore, both stearic and palmitic dhben imines act as efficient biodiesel antioxidants at room temperature and 50 °C, functioning as excellent metal chelators and free radical scavengers. However, stearic dhben demonstrated better performance as a metal chelator, whereas palmitic dhben was more effective as a free radical scavenger.

Long-term stability of molecular doped epigraphene quantum Hall standards: single elements and large arrays (R K/236 ≈ 109 Ω)

In this work we investigate the long-term stability of epitaxial graphene (epigraphene) quantum Hall resistance standards, including single devices and an array device composed of 236 elements providing R K/236 ≈ 109 Ω, with R K the von Klitzing constant. All devices utilize the established technique of chemical doping via molecular dopants to achieve homogenous doping and control over carrier density. However, optimal storage conditions and the long-term stability of molecular dopants for metrological applications have not been widely studied. In this work we aim to identify simple storage techniques that use readily available and cost-effective materials which provide long-term stability for devices without the need for advanced laboratory equipment. The devices are stored in glass bottles with four different environments: ambient, oxygen absorber, silica gel desiccant, and oxygen absorber/desiccant mixture. We have tracked the carrier densities, mobilities, and quantization accuracies of eight different epigraphene quantum Hall chips for over two years. We observe the highest stability (i.e. lowest change in carrier density) for samples stored in oxygen absorber/desiccant mixture, with a relative change in carrier density below 0.01% per day and no discernable degradation of quantization accuracy at the part-per-billion level. This storage technique yields a comparable stability to the currently established best storage method of inert nitrogen atmosphere, but it is much easier to realize in practice. It is possible to further optimize the mixture of oxygen absorber/desiccant for even greater stability performance in the future. We foresee that this technique can allow for simple and stable long-term storage of polymer-encapsulated molecular doped epigraphene quantum Hall standards, removing another barrier for their wide-spread use in practical metrology.

Assessing the Efficacy of A Mo2C/Peroxydisulfate System for Tertiary Wastewater Treatment: A Study of Losartan Degradation, E. coli Inactivation, and Synergistic Effects

This work examines the use of pristine Mo2C as an intriguing sodium persulfate (SPS) activator for the degradation of the drug losartan (LOS). Using 500 mg/L Mo2C and 250 mg/L SPS, 500 μg/L LOS was degraded in less than 45 min. LOS decomposition was enhanced in acidic pH, while the apparent kinetic constant decreased with higher LOS concentrations. According to experiments conducted in the presence of scavengers of reactive species, sulfate radicals, hydroxyl radicals, and singlet oxygen participated in LOS oxidation, with the latter being the predominant reactive species. The presence of competitors such as bicarbonate and organic matter reduced the observed efficiency in actual matrices, while, interestingly, the addition of chloride accelerated the degradation rate. The catalyst showed remarkable stability, with complete LOS removal being retained after five sequential experiments. The system was examined for simultaneous LOS decomposition and elimination of Escherichia coli. The presence of E. coli retarded LOS destruction, resulting in only 30% removal after 3 h, while the system was capable of reducing E. coli concentration by 1.23 log. However, in the presence of simulated solar irradiation, E. coli was reduced by almost 4 log and LOS was completely degraded in 45 min, revealing a significant synergistic effect of the solar/Mo2C/SPS system.

Desiccation induces varied responses within a soil bacterial genus.

Desiccation impacts a suite of physiological processes in microbes by elevating levels of damaging reactive oxygen species and inducing DNA strand breaks. In response to desiccation-induced stress, microbes have evolved specialized mechanisms to help them survive. Here, we performed a 128-day lab desiccation experiment on nine strains from three clades of an abundant soil bacterium, Curtobacterium. We sequenced RNA from each strain at three time points to investigate their response. Curtobacterium was highly resistant to desiccation, outlasting both Escherichia coli and a famously DNA damage-resistant bacterium, Deinococcus radiodurans. However, within the genus, there were also 10-fold differences in survival rates among strains. Transcriptomic profiling revealed responses shared within the genus including up-regulation of genes involved in DNA damage repair, osmolyte production, and efflux pumps, but also up-regulation of pathways and genes unique to the three clades. For example, trehalose synthesis gene otsB, the chaperone groEL, and the oxygen scavenger katA were all found in either one or two clades but not the third. Here, we provide evidence of considerable variation in closely related strains, and further elucidation of the phylogenetic conservation of desiccation tolerance remains an important goal for microbial ecologists.

Losses of methionol in PET-packed rosé wine in presence of SO2: Comparison between oxidation and scalping via uncertainty analysis

An uncertainty analysis was performed on a mechanistic model describing the transport and oxidation of methionol, a model aroma compound, in PET-packed rosé wine. This allowed to quantify the relative importance of the losses to the wine/packaging material (scalping) with respect to those due to oxidation over a year of storage. Additionally, the oxygen scavenging effect of SO2, was also evaluated. Results showed that the predictions of the wine concentrations of the three studied species –methionol, oxygen and SO2- are reasonable, and that the reaction pathway is largely dominant with respect to losses of methionol and SO2 through the wine/packaging interface. Contrarily, the oxidation reaction appears to be almost equally governed by the kinetic reaction constants and by the oxygen barrier properties of PET in some of the tested scenarios, and thus likely responsible of a large proportion of the uncertainty.

Tuning the Cathode-Electrolyte Interphase Chemistry with Multifunctional Additive for High-Voltage Li-Ion Batteries.

The utilization of layered oxides as cathode materials has significantly contributed to the advancement of the lithium-ion batteries (LIBs) with high energy density and reliability. However, the structural and interfacial instability triggered by side reactions when charged to high voltage has plagued their practical applications. Here, this work reports a novel multifunctional additive, id est, 7-Anilino-3-diethylamino-6-methyl fluoran (ADMF), which exhibits unique characteristics such as preferential adsorption, oxygen scavenging, and electropolymerization protection for high-voltage cathodes. The ADMF demonstrates the capability to ameliorate the growth of cathode-electrolyte interphase (CEI), effectively diminishing the dissolution of transition metal (TM) ions, reducing the interface impedance, and facilitating the Li+ transport. As a result, ADMF additive with side reaction-blocking ability significantly enhances the cycling stability of MCMB||NCM811 full-cells at 4.4V and MCMB||LCO full-cells at 4.55V, as evidenced by the 80% retention over 600 cycles and 87% retention after 750 cycles, respectively. These findings highlight the potential of the additive design strategy to modulate the CEI chemistry, representing a new paradigm with profound implications for the development of next-generation high-voltage LIBs.

Exploration of the effect and potential mechanism of quercetin in repairing spinal cord injury based on network pharmacology and in vivo experimental verification

Spinal cord injury (SCI) is a highly complex neurological disease, but there is no effective repair method. Quercetin is a flavonol drug and has a variety of biological activities, such as scavenging oxygen free radicals in the body to resist oxidation, inhibiting inflammation, and so on. In this study, quercetin was firstly demonstrated to reduce tissue damage, promote neuron survival and repair motor function after SCI in rats through in vivo experiments. Then, 293 potential targets of quercetin repair for SCI were predicted by network pharmacology. GO analysis revealed that the biological processes of potential targets focused mainly on signal transduction, negative regulation of the apoptotic process, protein phosphorylation, drug response, and so on. Similarly, KEGG analysis suggested that these potential targets were involved in cell growth regulation, differentiation, apoptosis, and a few metabolic pathways. PPI network analysis predicted that the key genes were EP300, CREBBP, SRC, HSP90AA1, TP53, PIK3R1, EGFR, ESR1, and CBL. Further, the molecular docking showed that quercetin binds well with these proteins. Finally, RT-qPCR and Western blotting experiments verified that quercetin downregulated the expression levels of PIK3R1 and EGFR. It is suggested that quercetin can repair SCI in rats through PI3K-AKT signaling pathway and EGFR/MAPK pathway, which may provide a new theoretical basis for the repair of spinal cord injury.

Advancing Bulk Metallic Glass Formation: Utilizing Rare-Earth Elements in Zr-Based Alloys

Zr-based bulk metallic glasses (BMGs) are characterized by excellent glass-forming ability, combined with superior mechanical properties. However, oxygen impurities degrade both these aspects as oxides serve as heterogeneous nucleation sites during solidification. Rare-earth elements (REEs) are known to be good oxygen scavengers, binding oxygen to less harmful forms. The most stable rare-earth oxide (REO) is M2O3, which occurs in three polymorphic forms, depending on the radius of metal cation: cubic, hexagonal, and monoclinic. Here, we show the effect of Sc, Y, Lu, Nd, and Gd additions in relation to the oxygen content on the glass-forming ability of the Zr52.5Cu17.9Ni14.6Al10Ti5 alloy. Microscopic observations (SEM) supported by chemical analysis (EDS, WDS), structure identification (XRD), and thermal analysis (DTA) were carried out. The critical diameter for glass formation (Dc) in the high oxygen alloy doped with cubic oxide-forming elements (Sc, Y, and Lu) can be even higher (Dc = 9 mm) compared to the undoped alloy synthesized from low oxygen components. Therefore, we have demonstrated that it is feasible to produce BMG using low-purity constituents with REE-based oxygen scavengers. This bridges the gap between laboratory development and cost-effective commercial applications.Graphical

Solute-induced grain refinement and defect suppression in boron-modified molybdenum manufactured via laser powder-bed fusion

Molybdenum manufactured with laser powder bed fusion (LPBF) has an undesirable coarse-grained, columnar microstructure interspersed with intergranular cracks, high porosity, and poor mechanical strength. These defects result from a combination of the harsh LPBF process conditions and the disadvantageous properties of molybdenum, such as its high brittle-ductile transition temperature and low tolerance for oxygen impurities. In order to suppress these defect-forming mechanisms and improve the suitability for LPBF, alloy-side material adjustments with simultaneous process optimization are necessary. In this work, the effect of adjusting Mo by adding 3.5 at.% B is investigated experimentally.Mo-3.5 at.% B specimens can be produced entirely free of cracks, with a density of 99.8%. The specimens have a microstructure of fine, equiaxed grains with an average grain size of 31 μm and an aspect ratio of 1.3, thus achieving substantial refinement of the otherwise typically coarse-grained columnar, anisotropic microstructure of pure Mo in LPBF. Furthermore, the grains possess a honeycomb-like cellular subgrain structure. This structure is formed through the solute rejection effect of B during the solidification and consists of initially solidified pure α-Mo cells with a cell size <1 μm and a honeycomb-like network of an ∼100 nm thick intercellular Mo2B phase completely covering the α-Mo cells. In addition, the formation of boron oxide inclusions, presumably B2O3, with a size of <50 nm within the Mo2B phase, provides an effective mechanism for scavenging oxygen impurities, thus ensuring segregation-free grain boundaries in Mo-3.5 at.% B.The microstructural modifications substantially improve the mechanical properties. Under appropriate process conditions, with the substrate plate preheating temperature playing a crucial role, a bending strength of 1120 ± 172 MPa and a hardness of 379 ± 24 HV10 at room temperature can be achieved. At a test temperature of 600 °C, an increase in the bending strength to 2265 MPa is observed, and the bending angle simultaneously increases from 2° at room temperature to 35° at 600 °C. These findings indicate that the strength of Mo-3.5 at.% B is limited by the brittle behavior of the material at lower temperatures, at which residual defects are likely to initiate fracture.

Electrodeposition of Microfabricated Rhenium-Filaments

Metallic filaments comprised of refractory materials are a necessary part of mass spectrometers used to measure isotopes. The current state-of-the-art material, rhenium, is formed into filaments using a mechanical crimper, limiting the accuracy, speed, and quantity of filaments that can be fabricated. The current work describes the development of wafer-scale, microfabricated Re filaments using silicon molds followed by electrodeposition of Re. The goal is to develop filaments with tight dimensional tolerances, high purity, and mechanical rigidity for the desired application and offer the ability to create 100’s-1000’s of filaments on a single silicon wafer.Electrodeposition of Re is notoriously difficult as the reduction potential of rhenium is close to the hydrogen evolution reaction in aqueous solutions.1 While rhenium has been successfully deposited from alkaline, acid, and concentrated lithium chemistries,2 the films are often thin, porous, and contain many impurities such as hydrogen and oxygen. Rhenium oxide is susceptible to reaction with moisture in the air, resulting in poor quality films with short functional lifetimes. To electroform precise, pure rhenium structures, hardier chemistries must be developed.The current work seeks to address this challenge using a water-in-salt chemistry (WISE) comprised of up to 4M lithium salts, complexing agents, reducing agents, and oxygen scavengers. Numerous physical agitation techniques were utilized to improve the quality of the film. Solutions were analyzed using various electrochemical techniques, UV-VIS, and Raman spectroscopy. The optimized chemistry was used to electrodeposit bulk batches of microfabricated 2mm x 300 um x 300 um filaments. The filaments were analyzed using microscopy, XRF, XRD, SEM, and EDS with a goal of use in high temperature mass spectrometry experiments. References (1) Naor, A.; Eliaz, N.; Burstein, L.; Gileadi, E. Direct Experimental Support for the Catalytic Effect of Iron-Group Metals on Electrodeposition of Rhenium. Electrochemical and Solid-State Letters 2010, 13 (12), D91. DOI: 10.1149/1.3489532.(2) Pappas, D. P.; David, D. E.; Lake, R. E.; Bal, M.; Goldfarb, R. B.; Hite, D. A.; Kim, E.; Ku, H.-S.; Long, J.; McRae, C. Enhanced superconducting transition temperature in electroplated rhenium. Applied Physics Letters 2018, 112 (18), 182601. Sandia National Laboratories is a multimission laboratory managed and operated by National Technology & Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA0003525. SAND2022-*****

Alleviating Manganese – Vanadium Redox Flow Batteries for Energy Storage and Subsequent Hydrogen Generation

Dual-circuit redox flow batteries (RFBs) consist of two discharging modes which has the potential to store energy beyond the capacity of the electrolytes in the form of hydrogen generation [1-3]. Inspired from the recent exploratory study by Reynard and Girault et al., this work focuses on utilizing Mn3+/Mn2+ (RFB catholyte ~ 1.51 V vs. SHE) in conjunction with V3+/V2+ (RFB anolyte ~ −0.26 V vs. SHE) as indirect redox mediators to drive mediated electrolysis of water in spatially separated external catalytic reactors [3]. The advantage of an additional layer to existing RFB is that a fully charged battery could potentially be chemically discharged particularly when green electricity is available in abundance to provide a secondary resource for energy such as hydrogen gas or other value-added commodity chemicals. However, Mn3+ is prone to rapid chemical disproportionation yielding Mn4+ which precipitates as MnO2(s) particles in acidic media, responsible for severe capacity fade during cycling. Studies in the literature suggest that oxygen scavenging additives such as V5+ is possibly the best defense mechanism to prevent MnO2 formation [4].In this study, the electrochemical behavior of Mn3+/Mn2+ couple in the favorable presence of V5+ is elucidated using cyclic voltammetry and ionic speciation diagrams. The voltammograms obtained under systematically varied conditions provide direct experimental evidence for competing redox reactions at the electrode surface. Nonetheless, the response measured from a macroelectrode mainly describes the quasi reversibility of the redox couple and gives little insight on electrode-electrolyte interface phenomenon. To obtain a more detailed picture of the diffusion layer, we employ carbon disk ultramicroelectrode (UME) for in-depth qualitative analysis. We anticipate that any deviation from the sigmoidal shape is an indication of a growing diffusion layer due to MnO2 passivation on the surface of electrode. Lastly, galvanostatic charge discharge profiles are obtained for Mn-V based redox flow battery with an aim to reveal the optimum state of charge because there exists a trade-off between the extent of Mn disproportionation within RFB during energy storage mode and volume of hydrogen gas produced during secondary mode. The knowledge obtained throughout the study will provide a fundamental understanding required for the rational design and development of aqueous electrochemical flow systems using Mn as the redox active species. Peljo, P., et al., All-vanadium dual circuit redox flow battery for renewable hydrogen generation and desulfurisation. Green Chemistry, 2016. 18(6): p. 1785-1797. Piwek, J., et al., Vanadium-oxygen cell for positive electrolyte discharge in dual-circuit vanadium redox flow battery. Journal of Power Sources, 2019. 439: p. 227075. Reynard, D. and H. Girault, Combined hydrogen production and electricity storage using a vanadium-manganese redox dual-flow battery. Cell Reports Physical Science, 2021: p. 100556. Reynard, D., et al., Vanadium-Manganese Redox Flow Battery: Study of MnIII Disproportionation in the Presence of Other Metallic Ions. Chemistry - A European Journal, 2020. 26.

Measurement of the radiation dose and radiation isocenter of the TrueBeam accelerator using 3D polymer gel dosimeters from the VIPAR family with different chemical history

This work describes the measurements of the ionizing radiation dose and the determination of the radiation isocenter using a tool consisting of three-dimensional polymer gel dosimeters and a dedicated software package. Specific polymer gel dosimeters were selected. Their inherent common feature is the possibility of high-resolution three-dimensional measurement of dose distribution in radiotherapy and the presence of the N-vinylpyrrolidone monomer in the composition alongside other substances such as the cross-linking agent N,N'-methylenebisacrylamide, oxygen scavengers, stabilizers and gel matrix. The aim of this study was to analyze the influence of the chemical history of N-vinylpyrrolidone (purity and aging) on the dose response of some dosimeters. In addition, this work seeks to answer the question of how important purity and aging of N-vinylpyrrolidone are in dosimetry applications, such as routine testing of medical accelerators.