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International journal of hydrogen energy 51건

  1. [해외논문]   Metabolic engineering of Rhodobacter sphaeroides for improved hydrogen production   SCI SCIE

    Ryu, M.H. , Hull, N.C. , Gomelsky, M.
    International journal of hydrogen energy v.39 no.12 ,pp. 6384 - 6390 , 2014 , 0360-3199 ,

    초록

    Rhodobacter sphaeroides 2.4.1 is a facultative photosynthetic purple nonsulfur bacterium that can generate hydrogen by using sunlight and organic carbon sources under anaerobic conditions. Hydrogen is produced by the nitrogenase. To optimize hydrogen production, we combined in a single strain several mutations known to enhance hydrogen production in anoxygenic phototrophic bacteria. The first metabolic engineering approach involved elimination of the major reductive pathways (electron sinks) that compete for electrons with the nitrogenase. A strain containing mutations in the pathways involving hydrogen uptake hydrogenase (hupSL), poly-β-hydroxybutyrate synthesis (phbC), and light harvesting complex-II (pucBA) showed significantly increased hydrogen production. The second approach involved increasing immediate electron flow to nitrogenase via the Rnf complex. This strategy resulted in modest improvements in hydrogen yield. The third approach involved upregulating nitrogenase expression and decoupling its expression from the presence of ammonium in the growth media. Mutations in the nifA gene, encoding the master transcriptional activator of nitrogen fixation genes, were found to be most effective for increasing total hydrogen yield, accelerating hydrogen production, and making this process tolerant to the presence of ammonia in the medium. The combination of beneficial mutations resulted in an additive and superior hydrogen producing strain of R. sphaeroides.

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  2. [해외논문]   Inhibitory effects of substrate and soluble end products on biohydrogen production of the alkalithermophile Caloramator celer: Kinetic, metabolic and transcription analyses   SCI SCIE

    Ciranna, A. , Ferrari, R. , Santala, V. , Karp, M.
    International journal of hydrogen energy v.39 no.12 ,pp. 6391 - 6401 , 2014 , 0360-3199 ,

    초록

    In this study the tolerance of the alkalithermophile Caloramator celer towards substrate (glucose) and soluble end product (acetate, formate and ethanol) inhibition was assessed employing nonlinear inhibition models. In addition, the effects of subinhibitory concentrations of end products on fermentative metabolism and regulation of 12 key genes involved in pyruvate catabolism were studied. Optimal growth and H 2 production were found at 50 mM of glucose and the critical substrate concentration was observed at 290-360 mM. Two inhibition models revealed that ethanol had a higher inhibitory effect on growth rate, whereas H 2 production kinetics was more sensitive towards increasing concentrations of acetate and formate. Acetate, the main soluble metabolite of the fermentation, inhibited the H 2 production by increasing the ionic strength in the medium. Subinhibitory concentrations of soluble end products induced changes in the metabolite profile of C. celer, specifically exogenous acetate (80 mM) and ethanol (40 mM) slightly increased the H 2 yield by 4 and 7%, respectively. However, despite the observed metabolic shifts, gene regulation was minimal and not always in agreement with the measured product yields. Overall, the results suggest that further optimization of the H 2 production process from C. celer should focus on methods to evolve adapted osmotolerant strains and/or remove soluble metabolites, especially acetate, from the culture.

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  3. [해외논문]   On the independence of hydrogen production from methanogenic suppressor in olive mill wastewater   SCI SCIE

    Goncalves, M.R. , Costa, J.C. , Pereira, M.A. , Abreu, A.A. , Alves, M.M.
    International journal of hydrogen energy v.39 no.12 ,pp. 6402 - 6406 , 2014 , 0360-3199 ,

    초록

    Anaerobic degradation of olive mill wastewater (OMW) at concentrations ranging from 2 to 100 g/L of chemical oxygen demand (COD) was assessed in batch assays. Methane was the main final product obtained for the lower concentrations tested. For 25 g COD/L, H 2 was temporarily produced, albeit H 2 depletion occurred, likely due to homoacetogenesis, since acetate was formed concomitantly. Hydrogen was produced and accumulated permanently in the assays containing 50 g COD/L of OMW. Methanogenesis and homoacetogenesis were naturally inhibited, suggesting that hydrogen recovery from OMW can be performed without the addition of methanogenic suppressors such as 2-bromoethanosulfonate. This fact opens new perspectives for the utilization of high OMW concentrations in a two-stage valorisation process combining biohydrogen and biomethane production.

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  4. [해외논문]   Sugarcane vinasse as substrate for fermentative hydrogen production: The effects of temperature and substrate concentration   SCI SCIE

    Lazaro, C.Z. , Perna, V. , Etchebehere, C. , Varesche, M.B.A.
    International journal of hydrogen energy v.39 no.12 ,pp. 6407 - 6418 , 2014 , 0360-3199 ,

    초록

    The present study aimed to evaluate the hydrogen production of a microbial consortium using different concentrations of sugarcane vinasse (2-12 g COD L -1 ) at 37 o C and 55 o C. In mesophilic tests, the increase in vinasse concentration did not significantly impact the hydrogen yield (HY) (from 1.72 to 2.23 mmol H 2 g -1 COD influent ) but had a positive effect on the hydrogen production potential (P) and hydrogen production rate (R m ). On the other hand, the increase in the substrate concentration caused a drop in HY from 2.31 to 0.44 mmol H 2 g -1 COD influent in the tests performed at 55 o C with vinasse concentrations from 2 to 12 g COD L -1 . The mesophilic community was composed of different species within the Clostridium genus, and the thermophilic community was dominated by organisms affiliated with the Thermoanaerobacter genus. Not all isolates affiliated with the Clostridium genus contributed to a high HY, as the homoacetogenic pathway can occur.

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  5. [해외논문]   Hydrogen production by Escherichia coli depends on glucose concentration and its combination with glycerol at different pHs   SCI SCIE

    Trchounian, K. , Sargsyan, H. , Trchounian, A.
    International journal of hydrogen energy v.39 no.12 ,pp. 6419 - 6423 , 2014 , 0360-3199 ,

    초록

    Escherichia coli produces molecular hydrogen (H 2 ) during glucose or mixed carbon (glucose and glycerol) fermentation. Dependence of H 2 production rate (V H"2 ) on glucose at different pHs was studied in a concentration dependent manner. During growth of wild-type on glucose, increasing glucose concentration from 0.05% to 0.2% resulted in the marked inhibition of V H"2 . Inhibitory effect of glucose was shown at pH 7.5 and 6.5 but not pH 5.5. However, glycerol added in the growth medium with 0.1% glucose significantly increased V H"2 but different effects at different pHs were established upon glucose or glycerol assays. The results indicate that H 2 production is inhibited by glucose in a concentration dependent manner during glucose fermentation but glucose in combination with glycerol might enhance H 2 production during mixed carbon fermentation.

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  6. [해외논문]   Characterization and catalytic performance of copper-based WGS catalysts derived from copper ferrite   SCI SCIE

    Lin, X. , Zhang, Y. , Yin, L. , Chen, C. , Zhan, Y. , Li, D.
    International journal of hydrogen energy v.39 no.12 ,pp. 6424 - 6432 , 2014 , 0360-3199 ,

    초록

    A series of copper ferrite-based catalysts were prepared by the co-precipitation method using KOH, K 2 CO 3 , Na 2 CO 3 , NaOH, and NaHCO 3 as the precipitants and their physicochemical properties were investigated by N 2 -physisorption, SEM, XRD, FT-IR, Raman, H 2 -TPR, N 2 O decomposition, and CO 2 -TPD. The characterization results indicated that the utilization of KOH as precipitant was favorable for the formation of copper ferrite, which exhibited smaller crystalline and higher reducibility. The catalytic test in the water-gas shift reaction (WGSR) revealed that the sample prepared with the KOH as precipitant exhibited higher activity and thermal stability than the other samples. It was suggested that higher Cu dispersion, larger amount of surface copper atoms, weak basic sites, and strong interaction between copper and iron oxides resulting from the copper ferrite were responsible for the high catalytic performance.

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  7. [해외논문]   Pd particle size effects on oxygen electrochemical reduction   SCI SCIE

    Zhou, W. , Li, M. , Ding, O.L. , Chan, S.H. , Zhang, L. , Xue, Y.
    International journal of hydrogen energy v.39 no.12 ,pp. 6433 - 6442 , 2014 , 0360-3199 ,

    초록

    A series of carbon-supported Pd nanoparticles catalysts with average sizes ranging from 2.7 to 8.7 nm was synthesized by an aqueous phase reduction method in the presence of citrate and evaluated for the oxygen reduction reaction (ORR). It was found that the average Pd particle size can be tuned and controlled by the citrate to Pd precursor ratio and the effect of citrate concentration on Pd particle sizes was carefully examined. The catalysts were also characterized by transmission electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopies, cyclic voltammetry and rotating disc electrode paleography. Measurements of the ORR activities using a rotating disk electrode show a monotonic increase in specific mass activity with increasing Pd dispersion. On the other hand, the specific surface activity displayed a volcano curve with the maximum value between 5.0 and 6.0 nm. The particle size effect could be attributed to a combination of several size-dependent effects, i.e. changes in the distribution of low index planes on the surface, the relative abundance of low coordination sites, and the Pd electronic states.

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  8. [해외논문]   Activity of Au/ZnO catalysts prepared by photo-deposition for the preferential CO oxidation in a H2-rich gas   SCI SCIE

    Dulnee, S. , Luengnaruemitchai, A. , Wanchanthuek, R.
    International journal of hydrogen energy v.39 no.12 ,pp. 6443 - 6453 , 2014 , 0360-3199 ,

    초록

    In this work, Au supported over ZnO prepared by photodeposition was applied to prepare nano-size Au catalysts by utilizing UV light for the preferential oxidation (PROX) of CO. The results demonstrated that Au can be dispersed homogeneously over ZnO in the size range of 1-2 nm with a narrow size distribution. It was clearly seen that the preparation parameters (i.e. irradiation time, precipitant concentration, calcination, and storage condition) had a significant effect on the catalytic activity. Among the variables studied, low concentrations of precipitant and long irradiation time were by far the most influential on the catalytic activity.

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  9. [해외논문]   Performance and stability of La0.5Sr0.5CoO3-δ perovskite as catalyst precursor for syngas production by partial oxidation of methane   SCI SCIE

    Morales, M. , Espiell, F. , Segarra, M.
    International journal of hydrogen energy v.39 no.12 ,pp. 6454 - 6461 , 2014 , 0360-3199 ,

    초록

    The aim of this work was to investigate the performance and stability of the perovskite La 0.5 Sr 0.5 CoO 3-δ , as a potential catalyst precursor, for the synthesis gas production by partial oxidation of methane. For this purpose, the catalytic activity of La 0.5 Sr 0.5 CoO 3-δ was studied as a function of the temperature, flow rate and feed composition. In addition, its stability with the time-on-stream and redox cycles was also explored. Before and after testing, the catalyst precursor was characterized by X-ray diffraction, SEM-EDX and specific surface area (BET). The results evidenced a remarkable catalytic activity due to the stability of the cobalt, which is in a highly disperse state, in its reduced state. The CH 4 conversion and the CO and H 2 selectivities were enhanced with the increase of redox cycles. Finally, the precursor was totally regenerated to the initial perovskite structure under a specific thermal treatment.

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  10. [해외논문]   Iron chelates as low-cost and effective electrocatalyst for oxygen reduction reaction in microbial fuel cells   SCI SCIE

    Nguyen, M.T. , Mecheri, B. , D'Epifanio, A. , Sciarria, T.P. , Adani, F. , Licoccia, S.
    International journal of hydrogen energy v.39 no.12 ,pp. 6462 - 6469 , 2014 , 0360-3199 ,

    초록

    Iron-chelated electrocatalysts for the oxygen reduction reaction (ORR) in a microbial fuel cell (MFC) were prepared from sodium ferric ethylenediamine-N,N'-bis(2-hydroxyphenylacetic acid) (FeE), sodium ferric diethylene triamine pentaacetic acid (FeD) supported on carbon Vulcan XC-72R carbon black and multi-walled carbon nanotubes (CNTs). Catalyst morphology was investigated by TEM; and the total surfaces areas as well as the pore volumes of catalysts were examined by nitrogen physisorption characterization. The catalytic activity of the iron based catalysts towards ORR was studied by cyclic voltammetry, showing the higher electrochemical activity of FeE in comparison with FeD and the superior performance of catalysts supported on CNT rather than on Vulcan XC-72R carbon black. FeE/CNT was used as cathodic catalyst in a microbial fuel cell (MFC) using domestic wastewater as fuel. The maximum current density and power density recorded are 110 (mA m -2 ) and 127 +/- 0.9 (mW m -2 ), respectively. These values are comparable with those obtained using platinum on carbon Vulcan (0.13 mA m -2 and 226 +/- 0.2 mW m -2 ), demonstrating that these catalysts can be used as substitutes for commercial Pt/C.

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