Stalagmite Al(OH)₃ growth on aluminum foil surface by catalytic CO₂ reduction with H₂O

Yoon, Hee Jung,Kim, Seog K.,Lee, Sung Woo,Sohn, Youngku Elsevier 2018 APPLIED SURFACE SCIENCE - Vol.450 No.-

<P><B>Abstract</B></P> <P>CO<SUB>2</SUB> reduction on a catalytic surface is a very attractive research for energy and environments. In the present study, CO<SUB>2</SUB> with H<SUB>2</SUB>O was found to be reduced to CO on an aluminum foil surface with evolution of H<SUB>2</SUB>, which resulted in the growth of stalagmite Al(OH)<SUB>3</SUB> on this surface. The reduction was found to be highly temperature dependent. The crystal growth and the changes in the crystal structure were confirmed by scanning electron microscopy, high resolution transmission electron microscopy, X-ray diffraction crystallography, FT-IR, and Raman spectroscopy. The surface chemical oxidation states were examined by Auger elemental mapping and X-ray photoelectron spectroscopy. The reaction mechanism was proposed to 2Al + CO<SUB>2</SUB> + 5H<SUB>2</SUB>O → 2Al(OH)<SUB>3</SUB> + CO + 2H<SUB>2</SUB>. The evolution of CO and H<SUB>2</SUB> was confirmed by gas-chromatography and gas sensors. These new findings highlight the potential of performing the reduction of CO<SUB>2</SUB> on a metal surface by understanding its surface reactions.</P> <P><B>Highlights</B></P> <P> <UL> <LI> CO<SUB>2</SUB> with H<SUB>2</SUB>O was reduced to CO on Al foil surface with evolution of H<SUB>2</SUB>. </LI> <LI> Stalagmite Al(OH)<SUB>3</SUB> was grown on Al foil surface. </LI> <LI> 2Al + CO<SUB>2</SUB> + 5H<SUB>2</SUB>O → 2Al(OH)<SUB>3</SUB> + CO + 2H<SUB>2</SUB> was proposed. </LI> <LI> GC, Sensor, SEM, HRTEM, XRD, Raman, XPS, Auger were used to confirm the result. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Hydrothermal growth of two dimensional hierarchical MoS₂ nanospheres on one dimensional CdS nanorods for high performance and stable visible photocatalytic H₂ evolution

Chava, Rama Krishna,Do, Jeong Yeon,Kang, Misook Elsevier 2018 APPLIED SURFACE SCIENCE - Vol.433 No.-

<P><B>Abstract</B></P> <P>The visible photocatalytic H<SUB>2</SUB> production from water splitting considered as a clean and renewable energy source could solve the problem of greenhouse gas emission from fossil fuels. Despite tremendous efforts, the development of cost effective, highly efficient and more stable visible photocatalysts for splitting of water remains a great challenge. Here, we report the heteronanostructures consisting of hierarchical MoS<SUB>2</SUB> nanospheres grown on 1D CdS nanorods referred to as CdS-MoS<SUB>2</SUB> HNSs as a high performance visible photocatalyst for H<SUB>2</SUB> evolution. The as-synthesized CdS-MoS<SUB>2</SUB> HNSs exhibited ∼11 fold increment of H<SUB>2</SUB> evolution rate when compared to pure CdS nanorods. This remarkable enhanced hydrogen evolution performance can be assigned to the positive synergetic effect from heteronanostructures formed between the CdS and MoS<SUB>2</SUB> components which assist as an electron sink and source for abundant active edge sites and in turn increases the charge separation. This study presents a low-cost visible photocatalyst for solar energy conversion to achieve efficient H<SUB>2</SUB>.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Hydrothermal synthesis was used for the fabrication of CdS-MoS<SUB>2</SUB> HNSs. </LI> <LI> Visible photocatalytic H<SUB>2</SUB> evolution studies were performed on CdS-MoS<SUB>2</SUB> HNSs. </LI> <LI> Enhanced H<SUB>2</SUB> evolution rate was observed for CdS-MoS<SUB>2</SUB> HNSs when compared to CdS NRs. </LI> <LI> MoS<SUB>2</SUB> nanospheres were successfully utilized as cocatalyst for H<SUB>2</SUB> evolution reaction. </LI> <LI> Charge recombination was suppressed in the CdS NRs by the concept of HNSs. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Fabrication of Ag based ternary nanocomposite system for visible-light photocatalytic hydrogen evolution reaction

Do, Jeong Yeon,Chava, Rama Krishna,Kim, Young Il,Cho, Dae Won,Kang, Misook Elsevier 2019 APPLIED SURFACE SCIENCE - Vol.494 No.-

<P><B>Abstract</B></P> <P>Solar driven visible photocatalytic H<SUB>2</SUB> evolution using semiconductors is recognized as one of the most promising routes for clean energy technology; however, efficient visible light utilization and charge separation are the key roles in a photocatalyst system for high activity. Herein, Ag based ternary nanocomposite system, Ag<SUB>2</SUB>S/Ag/Ag<SUB>3</SUB>VO<SUB>4</SUB> was synthesized by chemical reduction and subsequent hydrothermal methods. The prepared nanocomposites were characterized by Powder X-ray diffraction, X-ray photoelectron spectroscopy, Scanning and transmission electron microscopy, UV–vis diffuse reflectance and photoluminescence spectroscopy methods. The Ag<SUB>2</SUB>S/Ag/Ag<SUB>3</SUB>VO<SUB>4</SUB> ternary nanocomposite system displayed a higher photocatalytic H<SUB>2</SUB> evolution activity than that of pure Ag<SUB>3</SUB>VO<SUB>4</SUB>, Ag<SUB>2</SUB>S and their binary composites under visible light irradiation. In the present work, Ag<SUB>2</SUB>S/Ag/Ag<SUB>3</SUB>VO<SUB>4</SUB> exhibited a photocatalytic H<SUB>2</SUB> evolution activity of ~8.5 mmol·g<SUP>−</SUP> <SUP>1</SUP>. The enhanced photocatalytic activity can be attributed to the improved visible light absorption and effective charge separation between Ag<SUB>3</SUB>VO<SUB>4</SUB> and Ag<SUB>2</SUB>S via the electron shuttle mediator Ag.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Ag<SUB>2</SUB>S/Ag/Ag<SUB>3</SUB>VO<SUB>4</SUB> nanocomposite was designed for photocatalytic H<SUB>2</SUB> evolution reaction. </LI> <LI> H<SUB>2</SUB> evolution was accomplished even without electron sacrificial agent. </LI> <LI> Loading of Ag<SUB>2</SUB>S improved the optical absorption features. </LI> <LI> Improved charge separation efficiency was achieved. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Impact of Fermentation Rate Changes on Potential Hydrogen Sulfide Concentrations in Wine

( Butzke C. E. ),( Seung Kook Park ) 한국미생물 · 생명공학회 2011 Journal of microbiology and biotechnology Vol.21 No.5

The correlation between alcoholic fermentation rate, measured as carbon dioxide (CO2) evolution, and the rate of hydrogen sulfide (H2S) formation during wine production was investigated. Both rates and the resulting concentration peaks in fermentor headspace H2S were directly impacted by yeast assimilable nitrogenous compounds in the grape juice. A series of model fermentations was conducted in temperature-controlled and stirred fermentors using a complex model juice with defined concentrations of ammonium ions and/or amino acids. The fermentation rate was measured indirectly by noting the weight loss of the fermentor; H2S was quantitatively trapped in realtime using a pre-calibrated H2S detection tube which was inserted into a fermentor gas relief port. Evolution rates for CO2 and H2S as well as the relative ratios between them were calculated. These fermentations confirmed that total sulfide formation was strongly yeast strain-dependent, and high concentrations of yeast assimilable nitrogen did not necessarily protect against elevated H2S formation. High initial concentrations of ammonium ions via addition of diammonium phosphate (DAP) caused a higher evolution of H2S when compared with a non-supplemented but nondeficient juice. It was observed that the excess availability of a certain yeast assimilable amino acid, arginine, could result in a more sustained CO2 production rate throughout the wine fermentation. The contribution of yeast assimilable amino acids from conventional commercial yeast foods to lowering of the H2S formation was marginal.

Highly efficient hydrogen evolution catalysis based on MoS₂/CdS/TiO₂ porous composites

Du, Jimin,Wang, Huiming,Yang, Mengke,Zhang, Fangfang,Wu, Haoran,Cheng, Xuechun,Yuan, Sijie,Zhang, Bing,Li, Kaidi,Wang, Yina,Lee, Hyoyoung Elsevier 2018 International journal of hydrogen energy Vol.43 No.19

<P><B>Abstract</B></P> <P>Efficient production of hydrogen through visible-light-driven water splitting mechanism using semiconductor-based composites has been identified as a promising strategy for converting light into clean H<SUB>2</SUB> fuel. However, researchers are facing lots of challenges such as light absorption and electron-hole pair recombination and so on. Here, new sheet-shaped MoS<SUB>2</SUB> and pyramid-shaped CdS <I>in-situ</I> co-grown on porous TiO<SUB>2</SUB> photocatalysts (MoS<SUB>2</SUB> CdSTiO<SUB>2</SUB>) are successfully obtained <I>via</I> mild sulfuration of MoO<SUB>3</SUB> and CdO coexisted inside porous TiO<SUB>2</SUB> monolith by a hydrothermal route. The scanning electron microscopy and transmission electron microscopy results exhibit that the MoS<SUB>2</SUB> CdSTiO<SUB>2</SUB> composites have average pore size about 500 nm. The 3%MoS<SUB>2</SUB> 10%CdSTiO<SUB>2</SUB> demonstrated excellent photocatalytic activity and high stability for a hydrogen production with a high H<SUB>2</SUB>-generation rate of 4146 μmol h<SUP>−1</SUP> g<SUP>−1</SUP> under visible light irradiation even without noble-metal co-catalysts. The super photocatalytic performance of the visible-light-driven hydrogen evolution is predominantly attributed to the synergistic effect. The conduction band of MoS<SUB>2</SUB> facilitates in transporting excited electrons from visible-light on CdS to the porous TiO<SUB>2</SUB> for catalytic hydrogen production, and holes to MoS<SUB>2</SUB> for inhibiting the photocorrosion of CdS, respectively, leading to enhancing the efficient separation of electrons and holes.</P> <P><B>Highlights</B></P> <P> <UL> <LI> MoS<SUB>2</SUB>-CT photocatalysts have been successfully synthesized by two-step method. </LI> <LI> The porous structure can enhance photogenerated electron-hole pairs separation. </LI> <LI> The 3% MoS<SUB>2</SUB>-CT shows an excellent H<SUB>2</SUB> evolution rate of 4146 μmol h<SUP>−1</SUP> g<SUP>−1</SUP>. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

Nitrogen Defects-Rich 0D/2D α-Fe2O3/g-C3N4 Z-Scheme Photocatalyst for Enhanced Photooxidation and H2 Evolution Efficiencies

Chaocheng Zhao,Shuaijun Wang,Qingyun Yan,Pei Dong,Yongqiang Wang,Fang Liu,Lin Li 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2018 NANO Vol.13 No.7

Rational design and construction of Z-scheme photocatalysts have received much attention in the fields of organic pollutants degradation and H2 evolution because of their potentials to solve the current environmental and energy crises. Herein, a novel nitrogen defects-rich 0D/2D α-Fe2O3/g-C3N4 Z-scheme photocatalyst was fabricated via a one-pot co-pyrolysis method. Quantum-sized α-Fe2O3 dots with a diameter of approximately 5 nm were uniformly distributed on the surface of 2D g-C3N4. Besides, the prepared 0D/2D α-Fe2O3/g-C3N4 composites exhibited excellent RhB degradation ability and simultaneous H2 evolution efficiency. In comparison with 2D g-C3N4, the RhB degradation rate and H2 evolution catalyzed by 0D/2D α-Fe2O3/g-C3N4 were enhanced 3.9 and 1.8 times, respectively. The improved photoredox activity was predominantly attributed to the formation of the nitrogen defects and a Z-scheme heterojunction. This study provides novel insights into the design and fabrication of nitrogen defects-rich g-C3N4-based Z-scheme photocatalysts for the simultaneous environmental purification and H2 evolution.

Reduced graphene oxide as an efficient support for CdS-MoS₂ heterostructures for enhanced photocatalytic H₂ evolution

Ben Ali, Monaam,Jo, Wan-Kuen,Elhouichet, Habib,Boukherroub, Rabah Elsevier 2017 International journal of hydrogen energy Vol.42 No.26

<P><B>Abstract</B></P> <P>Cadmium sulphide nanorods-reduced graphene oxide-molybdenum sulphide(CdS-rGO-MoS<SUB>2</SUB>) composites were successfully synthesized using hydrothermal process for enhancing the interfacial contact between CdS nanorods and MoS<SUB>2</SUB> layer. The good contact between CdS and MoS<SUB>2</SUB> is important for improving the photocatalytic hydrogen (H<SUB>2</SUB>) evolution. The morphological and structural studies showed the production of highly pure CdS phase with nanorod-like structure dispersed on rGO-MoS<SUB>2</SUB> layer. X-ray photoelectron spectroscopy (XPS) and Raman results confirmed the reduction of graphene oxide (GO) into reduced graphene oxide (rGO). The higher photocurrent density of CdS-rGO-MoS<SUB>2</SUB> composites compared to CdS/MoS<SUB>2</SUB> and the fluorescence quenching observed for this composite provided some evidence for an inhibition of electron-hole recombination, which leads to a longer life time of the photogenerated carriers. Fast electron transfer can occur from CdS nanorods by the bidimensionnel rGO area to MoS<SUB>2</SUB> layer due to the intimate interfacial contact. Composite CdS-rGO-MoS<SUB>2</SUB> with 20 wt% rGO was found to be the most effective photocatalyst for H<SUB>2</SUB> evolution (7.1 mmol h<SUP>−1</SUP>g<SUP>−1</SUP>). The good photocatalytic performance arose from the positive synergistic effect between CdS, rGO and MoS<SUB>2</SUB> elements.</P> <P><B>Highlights</B></P> <P> <UL> <LI> CdS-rGO-MoS<SUB>2</SUB> composite was prepared by a hydrothermal technique. </LI> <LI> Reduced graphene oxide sheets led to a good adhesion between CdS and MoS<SUB>2</SUB>. </LI> <LI> Higher photocurrent density of CdS-rGO-MoS<SUB>2</SUB> composite is observed. </LI> <LI> The fluorescence of the nanocomposite was partially quenched. </LI> <LI> Good photocatalytic performance under visible light irradiation. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>

A stable and highly efficient visible-light-driven hydrogen evolution porous CdS/WO₃/TiO₂ photocatalysts

Qian, Yongteng,Yang, Mengke,Zhang, Fangfang,Du, Jimin,Li, Kaidi,Lin, Xialing,Zhu, Xinrui,Lu, Yayun,Wang, Weimin,Kang, Dae Joon Elsevier 2018 Materials characterization Vol.142 No.-

<P><B>Abstract</B></P> <P>It is well known that both catalytic efficiency and stability are the two important parameters of photocatalysts for visible-light-driven hydrogen production reactions. However, light-driven hydrogen evolution based applications still suffer from sluggish reaction kinetics due to the lack of high-performance photocatalysts. In this paper, we successfully synthesized a ternary porous CdS/WO<SUB>3</SUB>/TiO<SUB>2</SUB> photocatalyst with high efficiency and stability via two-stage approach. The as-prepared samples are characterized by XRD, FESEM, EDS, TEM, XPS, and UV–Vis, respectively, which illustrated that the CdS and WO<SUB>3</SUB> moieties are in-situ formed inside the porous TiO<SUB>2</SUB>. Particularly, the photocatalytic hydrogen (H<SUB>2</SUB>) evolution rate of such ternary 8% CdS/WO<SUB>3</SUB>/TiO<SUB>2</SUB> (molar ration of CdS:WO<SUB>3</SUB>:TiO<SUB>2</SUB> = 8:8:100) photocatalyst ranges up to 2106 μmol h<SUP>−1</SUP> g<SUP>−1</SUP> under visible-light irradiation, which is higher than that of pure TiO<SUB>2</SUB> and other binary (CdS/TiO<SUB>2</SUB> and WO<SUB>3</SUB>/TiO<SUB>2</SUB>) porous photocatalysts. The superior H<SUB>2</SUB> evolution efficiency can be attributed to the coexistence of CdS and WO<SUB>3</SUB> in porous TiO<SUB>2</SUB> which can promote the interfacial charge transfer and separation as well as extend the light absorption up to the visible range.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Highly efficient and stable photocatalytic activity of CdS/WO<SUB>3</SUB>/TiO<SUB>2</SUB> photocatalysts were synthesized by a two-step method. </LI> <LI> CdS and WO<SUB>3</SUB> inlaid on porous TiO<SUB>2</SUB> can extend the light absorption and enhance photogenerated electron-hole pairs separation. </LI> <LI> The porous structure can provide more reaction active sites and improve photoproduced-electrons and holes transport speed. </LI> </UL> </P> <P><B>Graphical Abstract</B></P> <P>[DISPLAY OMISSION]</P>

Functionality improvement of fungal lignin peroxidase by DNA shuffling for 2,4-dichlorophenol degradability and H₂O₂ stability

Ryu, K.,Hwang, S.Y.,Kim, K.H.,Kang, J.H.,Lee, E.K. Elsevier Science Publishers 2008 Journal of biotechnology Vol.133 No.1

One of the major problems of wild-type lignin peroxidase (LiP) is its inactivity at the presence of excess H<SUB>2</SUB>O<SUB>2</SUB> and high concentration of aromatic compounds. Little is known about the substrate-binding site of LiP, and functionality improvement of LiP was not actively tried by genetic engineering and directed evolution. In order to improve LiPs functionality, we performed directed evolution with a colorimetric screening method. Finally, three types of LiP mutants were screened. The catalytic efficiency of the variants toward 2,4-dichlorophenol (DCP) degradation activity and the stability against H<SUB>2</SUB>O<SUB>2</SUB> was increased over the wild type. The K<SUB>m</SUB> value of the variants toward H<SUB>2</SUB>O<SUB>2</SUB> was increased, but K<SUB>m</SUB> value toward 2,4-DCP degradation was reduced. Overall, The K<SUB>cat</SUB>/K<SUB>m</SUB> values of the mutants toward 2,4-DCP was increased ca. 4-fold, and that toward H<SUB>2</SUB>O<SUB>2</SUB> was increased ca. 89-fold. Amino acid sequence analysis indicated that the most of the mutations were located on the enzyme surface. We expect that these results coupled with recombining mutation can be successfully applied to the molecular evolution cycles for screening of LiPs and other oxidative enzymes with improved functionality and stability.

Flavobacterium odoratum의 TOL 플라스미드를 전달받은 광합성세균으로부터의 수소 생성

오순옥,조인성,이희경,민경희 한국미생물학회 1991 미생물학회지 Vol.29 No.6

TOL plsmid size of Flavobacterium odoratum SUB53 was estimated as 83 Md and the optimum concentration of m-toluate degradation by TOL plasmid was 5 mM. $H_{2}$ production by Rhodopseudomonas sphaeroides KCTC1425 was largely dependent on nitrogenase activity and showed the highest at 30 mM malate with 7 mM glutamate as nitrogen source. Nitrogenase activities were inhibited by 0.3 mM $NH_{4}^{+}$ions, to be appeared the decrease of $H_{2}$ production. Conjugation of TOL plasmids from F. odoratum SUB53 and Pseudomonas putida mt-2 to R. sphaeroides showed the optimum at the exponential stage of recipient cells in presence of helper plasmid pRK2013. According to the investigation of catechol-1,2-oxygenase (C-1, 2-O) and catechol-2,3-oxygenase (C-2,3-O) activities of R. sphaeroides C1 (TOL SUB53) and C2 (TOL mt-2), the gene for C-2,3-O is located on TOL plasmid and gene for C-1, 2-O on the chromosome of R. sphaeroides. m-Toluate was biodegraded by TOL plasmid in R. sphaeroides C1 and C2, presumably to be produced $H_{2}$ gas from the secondary metabolites of m-toluate.e.