• Title/Summary/Keyword: $pCO_2$

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Effect of pH on the Synthesis of $LiCoO_2$ with Malonic Acid and Its Charge/Discharge Behavior for a Lithium Secondary Battery

  • Kim, Do Hun;Jeong, Yu Deok;Kim, Sang Pil;Sim, Un Bo
    • Bulletin of the Korean Chemical Society
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    • v.21 no.11
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    • pp.1125-1132
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    • 2000
  • The pH effect of the precursor solution on the preparation of $LiCoO_2$ by a solution phase reaction containing malonic acid was carried out. Layered $LiCoO_2$ powders were obtained with the precursors prepared at the different pHs (4, 7, and 9) and heat-treated at $700^{\circ}C(LiCoO_2-700)$ or $850^{\circ}C(LiCoO_2-850)$ in air. pHs of the media for precursor synthesis affects the charge/discharge and electrochemical properties of the $LiCoO_2electrodes.$ Upon irrespective of pH of the precursor media, X-ray diffraction spectra recorded for $LiCoO_2-850$ powder showed higher peak intensity ratio of I(003)/I(104) than that of $LiCoO_2-700$, since the better crystallization of the former crystallized better. However, $LiCoO_2$ synthesized at pH 4 displayed an abnormal higher intensity ratio of I(003)/I(104) than those synthesized at pH 7 and 9. The surface morphology of the $LiCoO_2-850$ powders was rougher and more irregular than that of $LiCoO_2-700$ made from the precursor synthesized at pH 7 and 9. The $LiCoO_2electrodes$ prepared with the precursors synthesized at pH 7 and 9 showed a better electrochemical and charge/discharge characteristics. From the AC impedance spectroscopic experiments for the electrode made from the precursor prepared in pH 7, the chemical diffusivity of Li ions (DLi+) in $Li0.58CoO_2determined$ was 2.7 ${\times}$10-8 $cm^2s-1$. A cell composed of the $LiCoO_2-700$ cathode prepared in pH 7 with Lithium metal anode reveals an initial discharge specific capacity of 119.8 mAhg-1 at a current density of 10.0 mAg-1 between 3.5 V and 4.3 V. The full-cell composed with $LiCoO_2-700$ cathode prepared in pH 7 and the Mesocarbon Pitch-based Carbon Fiber (MPCF) anode separated by a Cellgard 2400 membrane showed a good cycleability. In addition, it was operated over 100 charge/discharge cycles and displayed an average reversible capacity of nearly 130 mAhg-1.

Production of Poly(3-hydroxybutyrate) by Cupriavidus necator at Various Concentrations of Carbon Dioxide (Cupriavidus necator를 이용한 Poly(3-hydroxybutyrate) 생산에 이산화탄소의 농도가 미치는 영향)

  • Park, Inseon;Jho, Eun Hea;Nam, Kyoungphile
    • Journal of Korean Society of Environmental Engineers
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    • v.35 no.2
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    • pp.109-114
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    • 2013
  • Polyhydroxyalkanoates (PHAs) are synthesized by numerous bacteria as carbon and energy storage compounds and are raw materials for biocompatible plastics. In this paper, the effect of $CO_2$ concentrations on the growth of C. necator and the accumulation of Poly(3-hydroxybutyrate) (P(3HB)) are investigated by increasing the $CO_2$ concentration in the substrate gas mixture. During 6 d cultivation in a nitrogen-present mineral medium, the $CO_2$ concentration did not affect the growth of the cells, while the Poly(3- hydroxybutyrate) (P(3HB)) content decreased with increasing $CO_2$ concentrations from 1% to 20%. During 4 d cultivation in the nitrogen-limited medium, the P(3HB) accumulation was the greatest at 3% $CO_2$; however, the total amount of accumulated P(3HB) was the greatest at 1% $CO_2$, which decreased with increasing $CO_2$ concentrations. The results indicate that the gas mixture with 1% $CO_2$ is the most effective in both growing the cells and accumulating P(3HB) under our experimental conditions.

Changes of carbon-13 Isotope of Dissolved Inorganic Carbon Within Low-pH CO2-rich Water during CO2 Degassing (pH가 낮은 탄산수의 CO2 탈기에 따른 용존탄소동위원소 변화)

  • Chae, Gitak;Yu, Soonyoung;Kim, Chan Yeong;Park, Jinyoung;Bang, Haeun;Lee, Inhye;Koh, Dong-Chan;Shinn, Young Jae;Oh, Jinman
    • Journal of Soil and Groundwater Environment
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    • v.24 no.3
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    • pp.24-35
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    • 2019
  • It is known that ${\delta}^{13}C_{DIC}$ (carbon-13 isotope of dissolved inorganic carbonate (DIC) ions) of water increases when dissolved $CO_2$ degases. However, ${\delta}^{13}C_{DIC}$ could decrease when the pH of water is lower than 5.5 at the early stage of degassing. Laboratory experiments were performed to observe the changes of ${\delta}^{13}C_{DIC}$ as $CO_2$ degassed from three different artificial $CO_2$-rich waters (ACWs) in which the initial pH was 4.9, 5.4, and 6.4, respectively. The pH, alkalinity and ${\delta}^{13}C_{DIC}$ were measured until 240 hours after degassing began and those data were compared with kinetic isotope fractionation calculations. Furthermore, same experiment was conducted with the natural $CO_2$-rich water (pH 4.9) from Daepyeong, Sejong City. As a result of experiments, we could observe the decrease of DIC and increase of pH as the degassing progressed. ACW with an initial pH of 6.4, ${\delta}^{13}C_{DIC}$ kept increasing but, in cases where the initial pH was lower than 5.5, ${\delta}^{13}C_{DIC}$ decreased until 6 hours. After 6 hours ${\delta}^{13}C_{DIC}$ increased within all cases because the $CO_2$ degassing caused pH increase and subsequently the ratio of $HCO_3{^-}$ in solution. In the early stage of $CO_2$ degassing, the laboratory measurements were well matched with the calculations, but after about 48 hours, the experiment results were deviated from the calculations, probably due to the equilibrium interaction with the atmosphere and precipitation of carbonates. The result of this study may be not applicable to all natural environments because the pressure and $CO_2$ concentration in headspace of reaction vessels was not maintained constant as well as the temperature. Nevertheless, this study provides fundamental knowledge on the ${\delta}^{13}C_{DIC}$ evolution during $CO_2$ degassing, and therefore it can be utilized in the studies about carbonated water with low pH and the monitoring of geologic carbon sequestration.

Effects of elevated CO2 concentration and increased temperature on leaf related-physiological responses of Phytolacca insularis (native species) and Phytolacca americana (invasive species)

  • Kim, Hae-Ran;You, Young-Han
    • Journal of Ecology and Environment
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    • v.33 no.3
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    • pp.195-204
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    • 2010
  • In the study, the effects of elevated $CO_2$ and temperature on the photosynthetic characteristics, chlorophyll content, nitrogen content, carbon content, and C/N ratio of Phytolacca insularis and Phytolacca americana were examined under control (ambient $CO_2+$ ambient temperature) and treatment (elevated $CO_2+$ elevated temperature) for 2 years (2008 and 2009). The photosynthetic rate, transpiration rate and water use efficiency of two plant species were higher under the treatment than the under the control. The stomatal conductance of P. insularis was higher under the control, but that of P. americana was not significantly affected by $CO_2$ and temperature under the treatment. The chlorophyll contents of two species were decreased about 72.5% and 20%, respectively, by elevated $CO_2$ and temperature. The nitrogen contents of two species were not significantly altered by increase in $CO_2$ and temperature. The carbon contents of the two species were higher under the treatment than under the control. The C/N ratio of P. insularis was higher under the treatment but that of P. americana was not significantly affected by $CO_2$ and temperature. These results demonstrated that the physiological responses of P. insularis native plants might be more sensitively influenced by a $CO_2$-mediated global warming situation than those of the P. americana invasive plants.

Triclinic Na3.12Co2.44(P2O7)2 as a High Redox Potential Cathode Material for Na-Ion Batteries

  • Ha, Kwang-Ho;Kwon, Mi-Sook;Lee, Kyu Tae
    • Journal of Electrochemical Science and Technology
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    • v.11 no.2
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    • pp.187-194
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    • 2020
  • Two types of sodium cobalt pyrophosphates, triclinic Na3.12Co2.44(P2O7)2 and orthorhombic Na2CoP2O7, are compared as high-voltage cathode materials for Na-ion batteries. Na2CoP2O7 shows no electrochemical activity, delivering negligible capacity. In contrast, Na3.12Co2.44(P2O7)2 exhibits good electrochemical performance, such as high redox potential at ca. 4.3 V (vs. Na/Na+) and stable capacity retention over 50 cycles, although Na3.12Co2.44(P2O7)2 delivered approximately 40 mA h g-1. This is attributed to the fact that Na2CoP2O7 (~3.1 Å) has smaller diffusion channel size than Na3.12Co2.44(P2O7)2 (~4.2 Å). Moreover, the electrochemical performance of Na3.12Co2.44(P2O7)2 is examined using Na cells and Li cells. The overpotential of Na cells is smaller than that of Li cells. This is due to the fact that Na3.12Co2.44(P2O7)2 has a smaller charge transfer resistance and higher diffusivity for Na+ ions than Li+ ions. This implies that the large channel size of Na3.12Co2.44(P2O7)2 is more appropriate for Na+ ions than Li+ ions. Therefore, Na3.12Co2.44(P2O7)2 is considered a promising high-voltage cathode material for Na-ion batteries, if new electrolytes, which are stable above 4.5 V vs. Na/Na+, are introduced.

Effect of Phosphorus Stress on Photosynthesis and Nitrogen Fixation of Soybean Plant under $CO_2$ Enrichment (대기 $CO_2$ 상승시 인산공급이 식물체의 광합성 및 질소고정에 미치는 영향)

  • Sa, Tong-Min
    • Applied Biological Chemistry
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    • v.40 no.2
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    • pp.134-138
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    • 1997
  • The objective of this study was to examine the effect of phosphorus deficiency on nitrogen fixation and photosynthesis of nitrogen fixing soybean plant under $CO_2$ enrichment condition. The soybean plants(Glycine max [L.] Merr.) inoculated with Bradyrhizobium japonicum MN 110 were grown with P-stressed(0.05 mM-P) and control(1 mM-P) treatment under control$(400\;{\mu}l/L\;CO_2)$ and enrichment$(800\;{\mu}l/L\;CO_2)$ enviromental condition in the phytotron equipped with high density lamp$(1000\;{\mu}Em^{-2}S^{-1})$ and $28/22^{\circ}C$ temperature cycle for 35 days after transplanting(DAT). At 35 DAT, phosphorus deficiency decreased total dry mass by 64% in $CO_2$ enrichment condition, and 51% in control $CO_2$ condition. Total leaf area was reduced significantly by phosphorus deficiency in control and enriched $CO_2$ condition but specific leaf weight was increased by P deficiency. Phosphorus deficiency significantly reduced photosynthetic rate(carbon exchange rate) and internal $CO_2$ concentration in leaf in both $CO_2$ treatments, but the degree of stress was more severe under $CO_2$ enrichment condition than under control $CO_2$ environmental condition. In phosphorus sufficient plants, $CO_2$ enrichment increased nodule fresh weight and total nitrogenase activity(acetylene reduction) of nodule by 30% and 41% respectively, but specific nitrogenase activity of nodule and nodule fresh weight was not affected by $CO_2$ enrichment in phosphorus deficient plant at 35 DAT. Total nitrogen concentrations in stem, root and nodule tissue were significantly higher in phosphorus sufficient plant grown under $CO_2$ enrichment, but nitrogen concentration in leaf was reduced by 30% under $CO_2$ enrichment. These results indicate that increasing $CO_2$ concentration does not affect plant growth under phosphorus deficient condition and phosphorus stress might inhibit carbohydrate utilization in whole plant and that $CO_2$ enrichment could not increase nodule formation and functioning under phosphorus deficient conditions and phosphorus has more important roles in nodule growth and functioning under $CO_2$ enrichment environments than under ambient condition.

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A Study on Characteristics of column fails in DDI DRAM (DDI DRAM에서의 Column 불량 특성에 관한 연구)

  • Chang, Sung-Keun;Kim, Youn-Jang
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.9 no.6
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    • pp.1581-1584
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    • 2008
  • In dual-polycide-gate structure with butting contact, net doping concentration of polysilicon was decreased due to overlap between $n^+$ and $p^+$ and lateral dopant diffusion in silicide/polysilicon layers. The generation of parasitic Schottky diode in butting contact region is attributed both to the $CoSi_2$-loss due to $CoSi_2$ agglomeration and to the decrease in net doping concentration of polysilicon layer. Parasitic Schottky diode reduces noise margin of sense amplifier in DDI DRAM, which causes column fail. The column fail could be reduced by physical isolation of $n^+/p^+$ polysilicon junction or suppressing $CoSi_2$ agglomeration by using nitrogen implantation into $p^+$ polysilicon before $CoSi_2$ formation.

A Study of the Formation of Carbon Monoxide in the Combustion of Anthracite Holed Briquettes (연탄이 연소할 때에 생성되는 일산화탄소에 대한 연구)

  • Han, Dong-Chin
    • Journal of the Korean Chemical Society
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    • v.11 no.4
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    • pp.150-158
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    • 1967
  • When anthracite burns by natural draft the mole percent of carbon monoxide (CO%) contained in exhaust gas is approximately expressed as follows in the early stage of combustion. (CO%)=$\frac{2{\alpha}}{1+{\alpha}}(CO_2%)$ exp $[-\vec{k}(No_2-Nc)^{1/2}{\tau}]$ where ${\alpha}=\frac{-0.395K_p+\sqrt{0.156K^2_p+(0.83+0.21K_p)K_p}}{0.83+0.21K_p}$ and $logK_p =-\frac{8593}{T} + 2.45logT -1.08{\times}10^{-3}T + 1.12{\times}10^{-7}T^2+2.77\vec{k},\;No_2$ and $N_c$ are the rate constant for the reaction ($CO+\frac{1}{2}O_2{\to}CO_2$), mole fraction of oxygen and oxides of carbon contained in the exhaust gas, respectively. From experimental evidence obtained in this work with natural draft combustion of briquettes the percent of carbon monoxide to the total quantity of oxides of carbon produced and rate of air flow into the furnace were: 1.76% and 0.53 l/sec (When lid is used in the furnace) 12.35% and 2.4 l/sec (without use of a lid). is the rate constant for the reaction($CO+\frac{1}{2}O_2{\to}CO_2$) and $N_0,\;and\;N_c$ are respectively the molefraction of oxygen and oxide of carbon contained in the exhaust gas.

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Interactive Effects of Increased Temperature and pCO2 Concentration on the Growth of a Brown Algae Ecklonia cava in the Sporophyte and Gametophyte Stages (갈조류 감태(Ecklonia cava)의 포자체와 배우체 생장에 영향을 주는 수온과 pCO2 농도의 상호작용)

  • Oh, Ji Chul;Yu, Ok Hwan;Choi, Han Gil
    • Ocean and Polar Research
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    • v.37 no.3
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    • pp.201-209
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    • 2015
  • To examine the effects of increased $CO_2$ concentration and seawater temperature on the photosynthesis and growth of forest forming Ecklonia cava (Laminariales, Phaeophyta), sporophytic discs and gametophytes were cultured under three $pCO_2$ concentrations (380, 750, 1000 ppm), four temperatures (5, 10, 15, $20^{\circ}C$ for sporophytes; 10, 15, 20, $25^{\circ}C$ for gametophytes), and two irradiance levels (40, $80{\mu}mol$ photons $m^{-2}s^{-1}$) for 5 days. Photosynthetic parameter values ($ETR_{max}$, $E_k$, and ${\alpha}$) were generally higher as sporophytic discs were grown under low temperature and increased $CO_2$ concentration at 750 ppm. However, photosynthesis of Ecklonia sporophytes was severely inhibited under a combination of high temperature ($20^{\circ}C$) and 1000 ppm $CO_2$ concentration at the two photon irradiance levels. The growth of gametophytes was maximal at the combination of 380 ppm (present seawater $CO_2$ concentration) and $25^{\circ}C$. Minimal growth of gametophytes occurred at enriched $pCO_2$ concentration levels (750, 1000 ppm) and high temperature of $25^{\circ}C$. The present results imply that climate change which is increasing seawater temperature and $pCO_2$ concentration might diminish Ecklonia cava kelp beds because of a reduction in recruitments caused by the growth inhibition of gametophytes at high $pCO_2$ concentration. In addition, the effects of increased temperature and $pCO_2$ concentration were different between generations - revealing an enhancement in the photosynthesis of sporophytes and a reduction in the growth of gametophytes.

Mechanism and Activation Parameters $({\Delta}H^{\neq},\;{\Delta}S^{\neq}$ and ${\Delta}V^{\neq})$ of Electron Transfer Reaction Between $Co^{II}CyDTA\;and\;Fe^{III}$CN Complex Ions (Co(II)-CyDTA와 Fe(III)-CN 착이온간의 전자이동반응에서 활성화파라미터 $({\Delta}H^{\neq},\;{\Delta}S^{\neq}$${\Delta}V^{\neq})$ 와 반응메카니즘)

  • Yu Chul Park;Seong Su Kim
    • Journal of the Korean Chemical Society
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    • v.33 no.3
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    • pp.273-280
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    • 1989
  • The spectra of the $Co^{II}CyDTA$(CyDTA: cyclohexyldiaminetetraacetic acid) complex have been measured in aqueous solution of pH = 6-13.2. The red shift of the spectrum in the more basic solution was ascribed to the transformation of $CoCyDTA^{2-}$ into $CoCyDTA(OH)^{3-}$. The equilibrium constant, $K_{OH} = [CoCyDTA(OH)^{3-}]/[CoCyDTA^{2-}][OH^-]$ was $75M^{-1}$ at $40^{\circ}C$. The electron transfer reactions of $CoCyDTA^{2-}$ and $CoCyDTA(OH)^{3-}$ with $Fe(CN)_6^{3-}$ have been studied using spectrophotometric technique in the range of pH applied to the determination of equilibrium constant. The pseudo first-order rate constants observed ($k_{obs}$) were not changed upto pH = 10.8, but increased with increasing pH in the range of pH = $10.8{\sim}13.0$. The rate law reduced in the range of pH = 6-13 was $k_{obs} = (k_3[CoCyDTA^{2-}] + k_4[CoCyDTA(OH)^{3-}])/(1+K_1[CoCyDTA^{2-}])$. The rate constants of the reactions (3a) and (3b), $k_3$ and $k_4$ respectively have been determined to be 0.529 and $4.500M^{-1}sec^{-1}$ at $40^{\circ}C$. The activation entropies (147{\pm}1.1JK^{-1} mol^{-1}$ at pH = 10.8) and activation volumes $(6.25cm^3mol^{-1}, pH = 10.8)$ increased with increasing pH, while the activation enthalpy (12.44 ${\pm}$ 0.20 kcal/mole) was independent of pH. Using the pH effect on the rate constants, the activation entropies and the activation volumes, the mechanism of the electron transfer reaction for $Co^{II}-Fe^{III}$ system was discussed.

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