Electrocatalysis for Energy Storage: Screening, Understanding and Improving Hydrogen Evolution Electrocatalysts in H2-Br2 Flow Batteries

In a transition from a society powered by greenhouse gas-emitting fossil fuels to one powered by renewable energy, energy storage can play a key role. Of the many technology options, one of the most promising is flow batteries, especially the hydrogen-bromine flow battery, which is the focus of this dissertation. To investigate the economic feasibility of a hydrogen-bromine battery as an energy storage device, the levelized cost of energy was calculated, and a sensitivity analysis indicated that the largest improvements to the cost of energy storage will come from improving the system lifetime and efficiency. The key scientific challenges to doing so require creating stable and efficient electrocatalysts. By electrochemically and chemically screening hundreds of metal sulfide materials selected based on our best chemical knowledge, ruthenium and rhodium based metal sulfides were determined to have sufficient stability to operate as hydrogen-bromine electrocatalysts, and exhibit promising activity for hydrogen evolution and oxidation. Incorporating cobalt and nickel into ruthenium sulfide greatly increased the electrocatalyst activity, which we came to understand through combined efforts of theory and gas-phase measurements. The increased activity is most likely due to increased rates of charge-transfer in the hydrogen evolution and oxidation reaction. However, even with incorporation of dopant atoms, the ruthenium sulfide compounds had relatively low hydrogen oxidation activity, possibly due to its semiconducting properties. Rhodium sulfide showed higher activity than even the best ruthenium sulfide materials, but still lower than platinum, although with much improved stability over platinum. Through selective synthesis of different rhodium sulfide phases, as well as poisoning experiments coupled with spectroscopy and density functional theory calculations, the activity of rhodium sulfide was determined to come from the metallic phases Rh17S15 and Rh3S4, in particular the metal sites on these compounds (rather than on sulfur atoms). By selectively forming these phases, the rhodium sulfide showed the highest activity, with the Rh2S3 and RhS2 phases showing low activity. Efforts to improve the rhodium sulfide by incorporation of dopant atoms were not as effective as for the ruthenium sulfide compounds, as transition metals such as Fe, Co, Ni and Cu caused the formation of an inactive rhodium thiospinel phase, and platinum group metal dopants showed no improvement in the rhodium sulfide on a metal sulfide-area basis. The greatest improvements in the activity of the electrocatalyst come from smaller particle sizes of Rh17S15 and Rh3S4 (increased dispersion), and minimization of inactive rhodium sulfide phases

Studies on crossability in cashew (Anacardium occidentale L.) genotypes

Successful hybridization primarily depends on the crossability of the parents involved as well as development of the F1 hybrids and their derivatives. In the present study, 12 crosses were attempted to study the crossability relationship among cashew genotypes. Among the crosses, the highest crossability was recorded in the cross H-303 x VTH 711/4 (17.16%), whereas, high rate of abscission of young fruits was observed in crosses involving NRCC Selection -2 as female parent. The genotype VTH 711/4 has shown substantially high per cent of crossability and better nut set with different genotypes of cashew

A RhxSy/C Catalyst for the Hydrogen Oxidation and Hydrogen Evolution Reactions in HBr

Rhodium sulfide (Rh2S3) on carbon support was synthesized by refluxing rhodium chloride with ammonium thiosulfate. Thermal treatment of Rh2S3 at high temperatures (600°C to 850°C) in presence of argon resulted in the transformation of Rh2S3 into Rh3S4, Rh17S15 and Rh which were characterized by TGA/DTA, XRD, EDX, and deconvolved XPS analyses. The catalyst particle size distribution ranged from 3 to 12 nm. Cyclic voltammetry and rotating disk electrode measurements were used to evaluate the catalytic activity for hydrogen oxidation and evolution reactions in H2SO4 and HBr solutions. The thermally treated catalysts show high activity for the hydrogen reactions. The exchange current densities (io) of the synthesized RhxSy catalysts in H2-saturated 1M H2SO4 and 1M HBr for HER and HOR were 0.9 mA/cm2 to 1.0 mA/cm2 and 0.8 to 0.9 mA/cm2, respectively. The lower io values obtained in 1M HBr solution compared to in H2SO4 might be due to the adsorption of Br− on the active surface. Stable electrochemical active surface area (ECSA) of RhxSy catalyst was obtained for CV scan limits between 0 V and 0.65 V vs. RHE. Scans with upper voltage limit beyond 0.65 V led to decreased and unreproducible ECSA measurements

Pattern of Tobacco Use and Perceived Risk of COVID-19 Following Tobacco Use among the COVID-19 Patients of a Tertiary Health Care Institution in Eastern India

Background: COVID-19 presented an unprecedented situation in which behavioural factors including tobacco use were believed to increase the risk of morbidity and mortality. The objective of the present study was to find the tobacco use pattern among the COVID-19 patients and the perceived risk of developing severe COVID-19 following tobacco use.Methods: This hospital-based, cross-sectional, analytical study was conducted among 300 COVID-19 patients at the All India Institute of Medical Sciences (AIIMS), Patna, India, during November and December 2020 using a semi-structured, pretested questionnaire. Descriptive and univariate analyses were performed using statistical software and the results were presented as proportion and percentage.Findings: About 27% and 16% of the COVID-19 patients were ever and current tobacco users, respectively. Quit attempts were found to have increased during the COVID-19 pandemic. A majority (65%) of current tobacco users had reduced their amount of tobacco use. Nearly 2 in every 3 patients perceived high risk of developing severe COVID-19 following tobacco use. Perceived risk was significantly higher among tobacco non-users, patients who were aware of the ill health effects of tobacco use, and patients who had noticed anti-tobacco messages or had been advised to quit tobacco. Among the current tobacco users, a significantly higher proportion of patients who perceived high risk of developing severe COVID-19 following tobacco use had made quit attempts or had reduced tobacco consumption during the pandemic (76.7% vs. 40%; P = 0.032).Conclusion: A high proportion of COVID-19 patients believed that tobacco use aggravated the COVID-19 condition. Increased quit attempts and reduction in tobacco consumption during this pandemic is a positive sign for tobacco contro

Drosophila Sirt2/mammalian SIRT3 deacetylates ATP synthase beta and regulates complex V activity

Adenosine triphosphate (ATP) synthase beta, the catalytic subunit of mitochondrial complex V, synthesizes ATP. We show that ATP synthase beta is deacetylated by a human nicotinamide adenine dinucleotide (NAD(+))-dependent protein deacetylase, sirtuin 3, and its Drosophila melanogaster homologue, dSirt2. dsirt2 mutant flies displayed increased acetylation of specific Lys residues in ATP synthase beta and decreased complex V activity. Overexpression of dSirt2 increased complex V activity. Substitution of Lys 259 and Lys 480 with Arg in human ATP synthase beta, mimicking deacetylation, increased complex V activity, whereas substitution with Gln, mimicking acetylation, decreased activity. Mass spectrometry and proteomic experiments from wild-type and dsirt2 mitochondria identified the Drosophila mitochondrial acetylome and revealed dSirt2 as an important regulator of mitochondrial energy metabolism. Additionally, we unravel a ceramide-NAD(+)-sirtuin axis wherein increased ceramide, a sphingolipid known to induce stress responses, resulted in depletion of NAD(+) and consequent decrease in sirtuin activity. These results provide insight into sirtuin-mediated regulation of complex V and reveal a novel link between ceramide and Drosophila acetylome

Survival response to increased ceramide involves metabolic adaptation through novel regulators of glycolysis and lipolysis

The sphingolipid ceramide elicits several stress responses, however, organisms survive despite increased ceramide but how they do so is poorly understood. We demonstrate here that the AKT/FOXO pathway regulates survival in increased ceramide environment by metabolic adaptation involving changes in glycolysis and lipolysis through novel downstream targets. We show that ceramide kinase mutants accumulate ceramide and this leads to reduction in energy levels due to compromised oxidative phosphorylation. Mutants show increased activation of Akt and a consequent decrease in FOXO levels. These changes lead to enhanced glycolysis by upregulating the activity of phosphoglyceromutase, enolase, pyruvate kinase, and lactate dehydrogenase to provide energy. A second major consequence of AKT/FOXO reprogramming in the mutants is the increased mobilization of lipid from the gut through novel lipase targets, CG8093 and CG6277 for energy contribution. Ubiquitous reduction of these targets by knockdown experiments results in semi or total lethality of the mutants, demonstrating the importance of activating them. The efficiency of these adaptive mechanisms decreases with age and leads to reduction in adult life span of the mutants. In particular, mutants develop cardiac dysfunction with age, likely reflecting the high energy requirement of a well-functioning heart. The lipases also regulate physiological triacylglycerol homeostasis and are important for energy metabolism since midgut specific reduction of them in wild type flies results in increased sensitivity to starvation and accumulation of triglycerides leading to cardiac defects. The central findings of increased AKT activation, decreased FOXO level and activation of phosphoglyceromutase and pyruvate kinase are also observed in mice heterozygous for ceramide transfer protein suggesting a conserved role of this pathway in mammals. These data reveal novel glycolytic and non-autonomous lipolytic pathways in response to increased ceramide for sustenance of high energy demanding organ functions like the heart

Risk of secondhand smoke exposure and severity of COVID-19 infection: multicenter case–control study

IntroductionExposure to secondhand smoke (SHS) is an established causal risk factor for cardiovascular disease (CVD) and chronic lung disease. Numerous studies have evaluated the role of tobacco in COVID-19 infection, severity, and mortality but missed the opportunity to assess the role of SHS. Therefore, this study was conducted to determine whether SHS is an independent risk factor for COVID-19 infection, severity, mortality, and other co-morbidities.MethodologyMulticentric case–control study was conducted across six states in India. Severe COVID-19 patients were chosen as our study cases, and mild and moderate COVID-19 as control were evaluated for exposure to SHS. The sample size was calculated using Epi-info version 7. A neighborhood-matching technique was utilized to address ecological variability and enhance comparability between cases and controls, considering age and sex as additional matching criteria. The binary logistic regression model was used to measure the association, and the results were presented using an adjusted odds ratio. The data were analyzed using SPSS version 24 (SPSS Inc., Chicago, IL, USA).ResultsA total of 672 cases of severe COVID-19 and 681 controls of mild and moderate COVID-19 were recruited in this study. The adjusted odds ratio (AOR) for SHS exposure at home was 3.03 (CI 95%: 2.29–4.02) compared to mild/moderate COVID-19, while SHS exposure at the workplace had odds of 2.19 (CI 95%: 1.43–3.35). Other factors significantly related to the severity of COVID-19 were a history of COVID-19 vaccination before illness, body mass index (BMI), and attached kitchen at home.DiscussionThe results of this study suggest that cumulative exposure to secondhand cigarette smoke is an independent risk factor for severe COVID-19 illness. More studies with the use of biomarkers and quantification of SHS exposure in the future are needed

Particle suspension reactors and materials for solar-driven water splitting

Reactors based on particle suspensions for the capture, conversion, storage, and use of solar energy as H_2 are projected to be cost-competitive with fossil fuels. In light of this, this review paper summarizes state-of-the-art particle light absorbers and cocatalysts as suspensions (photocatalysts) that demonstrate visible-light-driven water splitting on the laboratory scale. Also presented are reactor descriptions, theoretical considerations particular to particle suspension reactors, and efficiency and performance characterization metrics. Opportunities for targeted research, analysis, and development of reactor designs are highlighted