147 research outputs found
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
Selective and Low Overpotential Electrochemical CO2 Reduction to Formate on CuS Decorated CuO Heterostructure
Cu2O/CuO/CuS electrocatalyst was prepared by thermal oxidation of cleaned copper mesh in the air into Cu2O/CuO and CuS was deposited on oxide surface using facile successive ionic layer adsorption and reaction method. The successive fabrication of the electrocatalyst was confirmed using XRD, SEM, Raman and XPS. The catalytic enhancement is believed to be associated with the reduction of copper sulfide. Together with copper oxides, they offer favorable adsorption sites for electrochemical CO2 reduction. The synthesized catalyst offered significantly enhanced activity and selectivity performance for CO2 reduction at lower overpotential. Remarkably, the faradaic efficiency for formate generation reaches 84% at the potential of − 0.7 V versus RHE. It has also provided a high partial current density of − 20 mA cm− 2
Rechargeable Li/Cl battery down to -80 {\deg}C
Low temperature rechargeable batteries are important to life in cold
climates, polar/deep-sea expeditions and space explorations. Here, we report ~
3.5 - 4 V rechargeable lithium/chlorine (Li/Cl2) batteries operating down to
-80 {\deg}C, employing Li metal negative electrode, a novel CO2 activated
porous carbon (KJCO2) as the positive electrode, and a high ionic conductivity
(~ 5 to 20 mS cm-1 from -80 {\deg}C to 25 {\deg}C) electrolyte comprised of 1 M
aluminum chloride (AlCl3), 0.95 M lithium chloride (LiCl), and 0.05 M lithium
bis(fluorosulfonyl)imide (LiFSI) in low melting point (-104.5 {\deg}C) thionyl
chloride (SOCl2). Between room-temperature and -80 {\deg}C, the Li/Cl2 battery
delivered up to ~ 30,000 - 4,500 mAh g-1 first discharge capacity and a 1,200 -
5,000 mAh g-1 reversible capacity (discharge voltages in ~ 3.5 to 3.1 V) over
up to 130 charge-discharge cycles. Mass spectrometry and X-ray photoelectron
spectroscopy (XPS) probed Cl2 trapped in the porous carbon upon LiCl
electro-oxidation during charging. At lower temperature down to -80 {\deg}C,
SCl2/S2Cl2 and Cl2 generated by electro-oxidation in the charging step were
trapped in porous KJCO2 carbon, allowing for reversible reduction to afford a
high discharge voltage plateau near ~ 4 V with up to ~ 1000 mAh g-1 capacity
for SCl2/S2Cl2 reduction and up to ~ 4000 mAh g-1 capacity at ~ 3.1 V plateau
for Cl2 reduction. Towards practical use, we made CR2032 Li/Cl2 battery cells
to drive digital watches at -40 {\deg}C and light emitting diode at -80
{\deg}C, opening Li/Cl2 secondary batteries for ultra-cold conditions
Copper and Copper-Based Bimetallic Catalysts for Carbon Dioxide Electroreduction
Among many alternatives, CO2 electroreduction (CO2ER) is an emerging technology to alleviate its level in the atmosphere and simultaneously to produce essential products containing high energy density using various electrocatalysts. Cu-based mono- and bimetallics are electrocatalysts of concerns in this work due to the material's abundance and versatility. Intrinsic factors affecting the CO2ER are first analyzed, whereby understanding and characterizing the surface features of electrocatalysts are addressed. An X-ray absorption spectroscopy-based methodology is discussed to determine electronic and structural properties of electrocatalyst surface which allows the prediction of reaction mechanism and establishing the correlation with reduction products. The selectivity and faradaic efficiency of products highly depend on the quality of surface modification. Preparation and modification of electrocatalyst surfaces through various techniques are critical to increase the number of activity sites and the corresponding site activity. Mechanisms of CO2ER are complicate and thus are discussed in accordance with main products of interests. The authors try to concisely compile the most interesting, recent, and reasonable ideas that are agreeable to experimental results. Finally, this review provides an outlook for designing better Cu and Cu-based bimetallic catalysts to obtain selective products through CO2ER
Transformation of β-Ni(OH)2to NiO nano-sheets via surface nanocrystalline zirconia coating: Shape and size retention
Shape and size of the synthesized NiO nano-sheets were retained during transformation of sheet-like β-Ni(OH)2to NiO at elevated temperatures via nano-sized zirconia coating on the surface of β-Ni(OH)2. The average grain size was 6.42 nm after 600 °C treatment and slightly increased to 10 nm after 1000 °C treatment, showing effective sintering retardation between NiO nano-sheets. The excellent thermal stability revealed potential application at elevated temperatures, especially for high temperature catalysts and solid-state electrochemical devices
Identification of novel breast cancer susceptibility loci in meta-analyses conducted among Asian and European descendants
Abstract: Known risk variants explain only a small proportion of breast cancer heritability, particularly in Asian women. To search for additional genetic susceptibility loci for breast cancer, here we perform a meta-analysis of data from genome-wide association studies (GWAS) conducted in Asians (24,206 cases and 24,775 controls) and European descendants (122,977 cases and 105,974 controls). We identified 31 potential novel loci with the lead variant showing an association with breast cancer risk at P < 5 × 10−8. The associations for 10 of these loci were replicated in an independent sample of 16,787 cases and 16,680 controls of Asian women (P < 0.05). In addition, we replicated the associations for 78 of the 166 known risk variants at P < 0.05 in Asians. These findings improve our understanding of breast cancer genetics and etiology and extend previous findings from studies of European descendants to Asian women
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Identification of novel breast cancer susceptibility loci in meta-analyses conducted among Asian and European descendants
Abstract: Known risk variants explain only a small proportion of breast cancer heritability, particularly in Asian women. To search for additional genetic susceptibility loci for breast cancer, here we perform a meta-analysis of data from genome-wide association studies (GWAS) conducted in Asians (24,206 cases and 24,775 controls) and European descendants (122,977 cases and 105,974 controls). We identified 31 potential novel loci with the lead variant showing an association with breast cancer risk at P < 5 × 10−8. The associations for 10 of these loci were replicated in an independent sample of 16,787 cases and 16,680 controls of Asian women (P < 0.05). In addition, we replicated the associations for 78 of the 166 known risk variants at P < 0.05 in Asians. These findings improve our understanding of breast cancer genetics and etiology and extend previous findings from studies of European descendants to Asian women
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