• Title/Summary/Keyword: Hydrogen evolution rate

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A Study on Physiological conditions for hydrogen evolution by Rhodopseudomonass phaeroides K-7 (Rhodopseudomonas sphaeroides K-7에 의한 수소생성에 미치는 생리적 조건에 관한 연구)

  • Bae, Moo;Lee, Jeong-Kug
    • Korean Journal of Microbiology
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    • v.21 no.3
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    • pp.109-114
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    • 1983
  • Physiological conditions for hydrogen evolution by Rhodopseudomonas sphaeroides K-7 are examined. Larger amount of molecular hydrogen was evolved at $30^{\circ}C$, pH6.8-7.0 under anaerobically illuminated condition of about 12, 000 lux by the organism. The heighest rates of hydrogen evolution were observed in the culture with the organic acids such as acetate, DL-lactate or DL-malate in media containing L-glutamate as a nitrogen source. Hydrogen was also evolved from glucose with the rate of $178.9\;{\mu}l/hr/mg$ cells (dry weight). When glucose was adopted a a sole carbon source, however, conside erable time lag of about 20hours was required for hydrogen evolution. The resting cells stored at $30^{\circ}C$ under argon maintained the rate of hydrogen evolution in nearly about 90% of initial one even 40 days of storation.

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Thermal Analysis of Mg Hydride by Sievert's Type Automatic Apparatus (Sievert's type 자동장치에 의한 마그네슘 수소화합물의 열분석)

  • Han, Jeong Seb;Park, Kyung Duck
    • Korean Journal of Metals and Materials
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    • v.48 no.12
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    • pp.1123-1129
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    • 2010
  • In order to apply the Sievert's type automatic apparatus to thermal analysis of hydrogen absorbing materials, the dehydrogenation of the Mg-H system was investigated. As the initial wt% of hydrogen was increased to 4.4, the peak temperature of evolution rate shifted to higher temperature. However, with the initial wt% of hydrogen higher than 4.4, peak temperature of evolution rate did not change. The peak temperatures of evolution rate obtained by automatic apparatus were almost the same as those measured by a manual apparatus. As the heating rate was increased, the peak temperatures increased; the peak temperatures for heating rates 1, 2 and 3 K/min were 664, 687 and 702 K, respectively. The activation energy for the decomposition of Mg hydride was 101 kJ/mol. The Sievert's type automatic apparatus can be successively applied to the thermal analysis of metal hydride.

Effects of Zn-Flash Coating on Hydrogen Evolution, Infusion, and Embrittlement of Advanced-High-Strength Steel During Electro-Galvanizing (Zn-Flash 코팅 처리가 전기아연도금 시 초고강도 강재의 수소 발생, 유입 및 취화 거동에 미치는 영향)

  • Hye Rin Bang;Sang Heon Kim;Sung Jin Kim
    • Corrosion Science and Technology
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    • v.22 no.5
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    • pp.341-350
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    • 2023
  • In the present study, effects of a thin Zn-flash coating on hydrogen evolution, infusion, and embrittlement of advanced high strength steel during electro-galvanizing were examined. The electrochemical permeation technique in conjunction with impedance spectroscopy was employed under applied cathodic polarization. Moreover, a slow-strain rate test was conducted to evaluate loss of elongation (i.e., indicative of hydrogen embrittlement (HE)) and examine fracture surfaces. Results showed that the presence of a thin Zn-flash coating, even when it was not distributed uniformly, reduced hydrogen evolution rate and substantially impeded infusion of hydrogen into the steel substrate. This was primarily due to a hydrogen overvoltage on Zn coating and trapping of hydrogen at the interface of Zn coating/flash coating/steel substrate. Consequently, the sample with flash coating had a smaller HE index than the sample without flash coating. These results suggest that a thin Zn-flash coating could be an effective technical strategy for mitigating HE in advanced high-strength steels.

Hydrogen Evolution through Mixed Continuous Culture of Rhodopseudomonas sphaeroides and Clostridium butyricum (Rhodopseudomonas sphaeroides와 Clostridium butyricum의 혼합배양을 통한 수소생성의 연속발효계)

  • Go, Young-Hyun;Bae, Moo
    • Microbiology and Biotechnology Letters
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    • v.27 no.1
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    • pp.46-53
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    • 1999
  • The purpose of this study was to optimize the conditions of continuous mixed culture of C.butyricum and R. spaeroides K-7, which were able to produce hydrogen using biomass-dreived substrate. To investigate the possibility of continuous culture, semi-continuous culture was carried out for 20 days. In semi-continuous culture using the reactor system, the replacement rate of fresh medium was 30% of total medium volume for the highest hydrogen evolution. In continuous culture, the optimum dilution rate was determined to be 0.05$h^{-1}$. The continuous culture produced 3.1 times as compared with the hydrogen on batch culture. On the other hand, the continuous mixed culture produced 1.3~2.1 times as much as hydrogen of the continuous monoculture of C. butyricum. When 10g of glucose in the media (1l) was supplied as a carbon source on continuous culture, mixed culture of C. butyricum and R. sphaeroides K-7 increased hydrogen evolution rate. Because considerable amount of glutamate was contained in waste water of glutamate fermentation, utilization of glutamate was examined in mixed culture. As a result of examination, production of hydorgen was slightly inhibited by high concentration of glutamate, more than 20mM, on continuous monoculture of R. sphaeroides K-7. On the other hand, both on continuous monoculture of C. butyricum and on mixed culture of C. butyricum and R. sphaeroides K-7, production of hydrogen was not inhibited by high concentration of glutamate such as 100mM. Hence this suggests that high concentration of waste water can be used as good substrate for hydrogen production on monoculture of C. butyricum and mixed culture of C. butyricum and R. sphaeroides K-7.

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Thermal Analysis of LaNi5 Hydride by Volumetric Method (부피법 자동장치를 이용한 LaNi5 수소화합물의 열분석 장치개발)

  • HAN, JEONG-SEB;KIM, SUNJUNG
    • Transactions of the Korean hydrogen and new energy society
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    • v.29 no.1
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    • pp.25-31
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    • 2018
  • To apply Sievert's type apparatus to thermal analysis of hydrogen absorption materials, the dehydrogenation of $LaNi_5$ system was investigated. As the initial wt% of hydrogen was increased from 0.44 to 1.24 wt%, the peak temperature of evolution rate shifted to higher temperature. However, with the initial wt% of hydrogen higher than 0.95 wt%, the peak temperature of evolution rate did not change. As the heating rate was increased, the peak temperature increased; the peak temperatures for heating rates 0.5, 1.0 and 1.5 K/min were 262.2, 264.1, and 265.9 K respectively. The Sievert's type automatic apparatus can be successively applied to the thermal analysis of $LaNi_5$ hydride.

Platinum Decoration of a 3D Oxidized Graphitic Carbon Nitride/Graphene Aerogel for Enhanced Visible-Light Photocatalytic Hydrogen Evolution

  • Thi Kieu Oanh Nguyen;Thanh Truong Dang;Tahereh Mahvelati-Shamsabadi;Jin Suk Chung
    • Korean Chemical Engineering Research
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    • v.61 no.4
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    • pp.627-634
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    • 2023
  • Graphitic carbon nitride (g-C3N4) has attracted considerable attention since its discovery for its catalysis of water splitting to hydrogen and oxygen under visible light irradiation. However, pristine g-C3N4 confers only low photocatalytic efficiency and requires surface cocatalysts to reach moderate activity due to a lack of accessible surface active sites. Inspired by the high specific surface area and superior electron transfer of graphene, we developed a strongly coupled binary structure of graphene and g-C3N4 aerogel with 3D porous skeleton. The as-prepared 3D structure photocatalysts achieve a high surface area that favors efficient photogenerated charge separation and transfer, enhances the light-harvesting efficiency, and significantly improves the photocatalytic hydrogen evolution rate as well. The photocatalyst performance is observed to be optimized at the ratio 3:7 (g-C3N4:GO), leading to photocatalytic H2 evolution of 16125.1 mmol. g-1. h-1 under visible light irradiation, more than 161 times higher than the rate achieved by bulk g-C3N4.

Effect of Electrolyte-Additives on the Performance of Al-Air Cells (전해질 첨가제가 알루미늄-공기전지의 성능에 미치는 영향)

  • Park, Gwun Pil;Chun, Hai Soo
    • Applied Chemistry for Engineering
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    • v.9 no.1
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    • pp.52-57
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    • 1998
  • The effects of additives such as zinc compounds in 4M KOH electrolyte of Al-air cell have been studied. Zinc compounds in electrolyte increased hydrogen evolution overpotential and TPC(tripotasium citrate)/CaO formed fine film on aluminum surface, and these additives decreased hydrogen evolution rate and corrosion rate of aluminum. These additives shifted the OCP in the positive direction on high purity aluminum(purity, 99.999%) and in the negative direction on Al No 1050(purity,99.5%). Addition of two or more additives resulted in the prevention or the reduction of corrosion rate and hydrogen evolution at OCP. As the overpotential on Al electrode increased, the hydrogen evolution rate decreased and the utilization of aluminum increased. At high current density$(>100mA/cm^2)$, TPC/CaO/ZnO additives increased the utilization of high purity aluminum up to that of aluminum alloys containing indium, gallium and thallium.

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Photochemical hydrogen production from coupled semiconductor systems : CdS-WO3/RuO2, CdS-TiO2 (혼합반도체 시스템에서의 광화학적 수소제조 : CdS-WO3/RuO2, CdS-TiO2)

  • Suh, J.K.;Heo, G.S.
    • Transactions of the Korean hydrogen and new energy society
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    • v.4 no.2
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    • pp.5-15
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    • 1993
  • Hydrogen production in visible light with the following semiconductor systems, $CdS-WO_3$, $CdS-TiO_2$, have been investigated in the presence of redox catalyst (Pt, $RuO_2$). MeOH, EtOH, isopropanol, sulfide/sulfite mixture, lactic acid were used as sacrifical reagents. The optimal condition for $H_2$ evolution was found to be in qgueous lactic acid media for $CdS-WO_3/RuO_2$. The photochemical efficiency for this system was 1.05 % and the $H_2$ evolution rate was 26.5ml/min. at $6.07{\times}10^{-5}$ einstein/sec photon rate

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Volumetric Thermal Analysis of Hydrogen Desorption from Mg-13.5wt%Ni Hydride (Mg-13.5wt%Ni 합금 수소화합물의 수소방출에 대한 부피법에 의한 열분석)

  • HAN, JEONG SEB;PARK, KYUNG DUCK
    • Transactions of the Korean hydrogen and new energy society
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    • v.26 no.4
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    • pp.308-317
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    • 2015
  • To investigate the effect of microstructure on the formation of the desorption peak, the volumetric thermal analysis technique (VTA) was applied to the Mg-13.5 wt% Ni hydride system. The sample made by the HCS (hydriding combustion synthesis) process had two kinds of Mg microstructures. Linear heating was started with various constant heating rates. Only one peak was appeared in the case of the small initial hydrogen wt% (0.83 wt%). Yet, two peaks were appeared with increasing initial hydrogen wt% (1.85 and 3.73 wt%) when only Mg was hydrogenated. The first peak was formed through the evolution of hydrogen from $MgH_2$, made by eutectic Mg. The second peak was formed through the evolution of hydrogen from $MgH_2$, made by primary Mg. Therefore, this result shows that the microstructure also has a considerable effect on forming the desorption peak. We have also derived the hydrogen desorption equations by VTA to get apparent activation energy when the rate-controlling step for the desorption of the hydrided system is the diffusion of hydrogen through the ${\alpha}$ phase and the chemical reaction ${\beta}{\rightarrow}{\alpha}$.

Pyrolysis Behavior of Pulverized Coal Particles at High Heating Rate (미분탄 입자의 고속가열 열분해거동 해석)

  • JANG, JIHOON;HAN, KARAM;YU, GEUN SIL;LIM, HYEON SOO;LEE, WOOK RYUN;PARK, HO YOUNG
    • Transactions of the Korean hydrogen and new energy society
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    • v.30 no.3
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    • pp.260-268
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    • 2019
  • The pyrolysis characteristics of pulverized coal particle was numerically analyzed with the drop tube furnace. Based on the simulated gas flow field in the drop tube furnace, the particle velocity, temperature and volatile evolution were calculated with the fourth order Runge-Kutta method. The effects of changes in reactor wall temperature and particle diameter on the pyrolysis behavior of coal particle were investigated. The particle heating rate was very sensitive to the reactor wall temperature and particle size, that is, the higher wall temperature and the smaller particle size resulted in the higher heating rate and the consequent quicker volatile evolution.